Atari* System Reference manual
(c) 1987 By Bob DuHamel
Bob Duhamel
6915 Casselberry Way
San Diego, CA 92119
*Atari is a registered trademark of Atari Corp.
This manual contains highly technical information. Such information
is provided for those who know how to use it. To understand the
advanced information you are expected to know 6502 assembly language.
If you are new to programming, concentrate on the parts which discuss
BASIC commands.
Addresses are usually given in both hexadecimal and decimal numbers.
The operating system equate names are given in capital letters with
the address following in brackets. The decimal address is in
parenthsis within the brackets. For example:
DOSVEC [$000A,2 (10)]
name hex dec
The ",2" after the hexadecimal number means that this address requires
two bytes to hold its' information. Any address called a "vector"
uses two bytes whether noted or not.
Control registers and some other bytes of memory are shown in the
following format
Register format
7 6 5 4 3 2 1 0
-----------------
| |
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
The numbers on top are the bit numbers. Bit 7 is the Most Significant
Bit (MSB) and bit 0 is the Least Significant bit (LSB). The numbers
on the bottom are the bit weights. These are useful when changing
memory with decimal numbers, as you would in BASIC. For example, to
set bit 4 of a register to 1, without changing any other bits you
would add 16 to the decimal number already in the register. To reset
the same bit to 0, you would subtract 16 from the number in the
register. This is exactly what the command GRAPHICS 8+16 does. It
sets bits 3 and 4 of a graphics mode control register.
MSB and LSB may also mean Most Significant Byte or Least Significant
Byte, depending on context.
CONTENTS
1 THE CENTRAL INPUT/OUTPUT UTILITY, (CIO)
2 THE DISK OPERATING SYSTEM (D:)
3 USING THE DOS 2 UTILITIES (DUP.SYS)
4 THE CASSETTE HANDLER (C:)
5 THE KEYBOARD HANDLER (K:)
6 PRINTER HANDLER (P:)
7 SCREEN EDITOR (E:)
8 THE DISPLAY HANDLER (S:)
9 THE RESIDENT DISK HANDLER
10 SYSTEM INTERRUPTS
11 THE FLOATING POINT ARITHMETIC PACKAGE
12 BOOT SOFTWARE FORMATS
13 THE SERIAL INPUT/OUTPUT INTERFACE (SIO)
14 THE HARDWARE CHIPS
15 DISPLAY LISTS
16 PLAYER AND MISSILE (PM) GRAPHICS
17 SOUND
18 THE JOYSTICK PORTS
19 MISC
20 THE XL AND XE MODELS
CHAPTER 1
THE CENTRAL INPUT/OUTPUT UTILITY, (CIO)
The ATARI computer uses a very easy-to-use input and output
system called the Central Input/Output utility, or CIO. Nearly all
input or output passes through this utility.
CIO uses eight "channels" as paths for I/O. There are not really
separate channels for I/O but the computer acts as if there were.
Each channel is controlled by a 16 byte block of memory called an
Input/Output Control Block or IOCB. The channels are used by putting
the proper numbers in the proper IOCB bytes then jumping to the CIO
routine. In BASIC, complete I/O operations can be as easy as typing a
command such as LPRINT. In this case BASIC does all the work for
you.
THE CIO CHANNELS
There are eight CIO channels, numbered from 0 to 7. In BASIC some
channels are reserved for BASIC's use.
BASIC CIO channel assignments
Channel 0 Permanently assigned to the screen editor
6 Used for graphics commands
7 Used for the Cassette, disk and printer
Channels 6 and 7 are free to use when they are not being used by
BASIC. With machine language, all of the channels are available to
the programmer.
THE IOCB STRUCTURE
The IOCB for channel zero starts at address $0340 (decimal 832). This
is the only address you need to know. Indexing from this address is
used to find all of the other bytes. Below are the names and uses of
the IOCB bytes.
IOCB bytes and uses:
ADDRESS NAME EXPLANATION
$0340 ICHID handler Identifier
$0341 ICDNO device number (disk)
$0342 ICCOM command
$0343 ICSTA status
$0344 ICBAL buffer address (low byte)
$0345 ICBAH buffer address (high byte)
$0346 ICPTL address of put byte
$0347 ICPTH routine (used by BASIC)
$0348 ICBLL buffer length (low byte)
$0349 ICBLH buffer length (high byte)
$034A ICAX1 auxiliary information
$034B ICAX2 -
$034C ICAX3 the remaining auxiliary
$034D ICAX4 bytes are rarely used
$034E ICAX5 -
$034F ICAX6 -
ICHID
When a channel is open, the handler I.D. contains an index to the
handler table. The handler table (to be discussed later) holds the
address of the device handling routines. When the channel is closed
ICHID contains $FF.
ICDNO
The device number is used to distinguish between multiple devices with
the same name, such as disk drives.
ICCOM
The command byte tells CIO what operation to perform.
CIO command codes
HEX DEC
+Open $03 3
+close $0C 12
get $07 7
put $09 11
input $05 5
print $09 9
+status
request $0D 13
+*special >$0D >13
+ command may be made to a closed channel
* device specific commands
ICSTA
The status byte contains an error code if something goes wrong. If
bit 7 is 0 there have been no errors.
ICBAL and ICBAH
Before a channel is opened, the buffer address bytes are set point to
the block of memory which contains the name of the device the channel
is to be opened to. Before actual input or output these bytes are set
to point to the block of memory where the I/O data is stored or is to
be stored.
ICPTL and ICPTH
The put routine pointer is set by CIO to point to the handlers'
put-byte routine. When the channel is closed the pointer points to
the IOCB-closed routine. This pointer is only used by BASIC.
ICBLL and ICBLH
The buffer length bytes show the number of bytes in the block of
memory used to store the input or output data. (See ICBAL and ICBAH.)
If the amount of data read during an input operation is less than the
length of the buffer, the number of bytes actually read will be put in
ICBLL and ICBLH by CIO.
ICAX1 through ICAX6
The auxiliary information bytes are used to give CIO or the device any
special information needed.
OPENNING A CIO CHANNEL
Before using a CIO channel it must be assigned to an I/O device. In
machine language you start by putting the channel number in the four
high bits of the 6502 X register (X = $30 for channel three). Next
you place the necessary codes (parameters) into IOCB 0 indexed by X.
The X register will cause the numbers to be offset in memory by 16
times the channel number. This puts the numbers into the correct IOCB
instead of IOCB 0. Below are the parameters used to open a channel.
Channel-open parameters:
ICCOM open code
ICBAL address of device name
ICBAH in memory
ICAX1 direction code
ICAX2 zero
The direction code byte in ICAX1 takes on the following format:
ICAX1 format for opening a channel
7 6 5 4 3 2 1 0
-----------------
ICAX1 | W R |
-----------------
8 4 2 1
W 1 = open for output (write)
R 1 = open for input (read)
ICAX1 may have the following data
CIO direction codes
HEX DEC operation
$04 4 input
$08 8 output
$0C 12 input and output (cannot change the length
of a disk file)
ICBAL and ICBAH point to the device name stored in memory. The device
and file name must be followed by 0 or $9B (decimal 155).
Once the parameters are set, jumping (JSR) to the CIO vector
(CIOV) at address $E456 (58454) will cause the channel to be opened.
In the following example a basic knowledge of assembly language is
assumed.
Routine to open channel 1 to the keyboard:
ICHID = $0340
ICCOM = ICHID+2
ICAX1 = ICHID+10
ICAX2 = ICHID+11
IOCB1 = $10 channel in four high bits
CIOV = $E456
OPEN = $03
OREAD = $04 ;open for input
ERROR = (address of error handling routine)
;
START LDX IOCB1
LDA OPEN
STA ICCOM,X
LDA NAME
STA ICBAH,X
LDA OREAD
STA ICAX1,X
LDA #0
STA ICAX2,X
JSR CIOV
BPL OK
JMP ERROR
;
NAME .BYTE "K:",$9B
OK (program continues here)
To open a CIO channel in BASIC the OPEN command is used.
BASIC OPEN command format:
OPEN #channel,aux1,aux2,device:file name
aux1 = direction code
aux2 = special code
To open channel 1 to the keyboard in BASIC Type:
OPEN #1,4,0,"K:"
The third parameter, aux2, is a rarely used special parameter. One
use is to keep the screen from erasing when changing graphics modes.
The fourth parameter is the device to open the channel to. It may be
either a string in quotes or a string variable.
CIO device names
C cassette recorder
*D disk drive
E screen editor
K Keyboard
P printer
*R RS 232 I/O port
S screen handler
* Uses a non-resident handler loaded by the device at
power-up.
The device name must usually be followed by a colon. With the disk
drive a file name is expected after the device name. The screen
handler is used for graphics. The screen editor uses both the
keyboard handler and the screen handler to work between the keyboard
and screen.
USING AN OPEN CHANNEL
Once a channel is opened to a device you have several options:
INPUT: (ICCOM = $05)
The computer reads data from the device until a carriage-return is
read (decimal number 155, hex $9B) or the end of the file (EOF) is
reached. A carriage return is also known as an End-Of-Line or EOL.
The IOCB input parameters are:
IOCB input parameters:
ICCOM get record code
ICBAL address of buffer to
ICBAH store the data in
ICBLL length of the data
ICALH buffer
The following routine demonstrates the input command in assembly
language. Some of the equates are in the channel openning example
above.
Input routine:
GETREC = $05
BUFF = (address to store data at)
BUFLEN = (number of bytes available at storage address)
:
LDX IOCB1
LDA GETREC
STA ICCOM,X
LDA < BUFF
STA ICBAL,X
LDA > BUFF
STA ICBAH,X
LDA < BUFLEN
STA ICBLL,X
LDA > BUFLEN
STA ICBLH,X
JSR CIOV
BPL OK2
JMP ERROR
:
OK2 (continues if no errors)
If the data retrieved is shorter than the prepared buffer, the number
of bytes actually read will be put into ICBLL and ICBLH.
In BASIC, the INPUT command is used.
BASIC INPUT command format:
INPUT #channel,string variable
or
INPUT #channel,arithmetic variable
For example:
INPUT #1,IN$
The above commands will cause the data from the device to be put into
the specified buffer (IN$ in the BASIC example) until an EOL is
reached. If the INPUT statement is used again, without closing the
channel, the computer will get more data from the device until another
EOL is read or the end of the file is reached. The new data will
write over the old data in the input string or buffer. If an
arithmetic variable is used, only numbers can be input.
PRINT: (ICCOM = $09)
In assembly language the print command is identical to the input
command. The only difference is that the PUTREC code ($09) is stored
in ICCOM. Of course the buffer bytes of the IOCB then specify the
block of memory to be output from rather than input to. With the
print command, EOLs within the string or buffer are ignored but an EOL
is placed at the end of the data when sent to the device.
In BASIC, the PRINT command is used like INPUT except you want to use
a semicolon instead of a comma to separate parameters. For example:
PRINT #1;OUT$
or
PRINT #1;"HELLO"
If you use a comma, ten space characters will be sent before the
string.
If the print command is used again, without closing the channel, the
new data will be appended to the end of the data previously sent. Old
data will not be written over.
GET: (ICCOM = $07)
In BASIC this command inputs a single byte of data from the device.
EOLs are ignored. In BASIC, GET is used like INPUT except an
arithmetic variable must be used. For example:
GET #1,IN
If the get command is used again the next byte from the device will be
read. If the end of a file is reached an error will occur.
There is no command in BASIC to input an entire file without stopping
at each EOL. If you wish to ignore EOLs while reading a file to a
string, you must use the GET command. Each byte of data is then put
into the string by the program.
EXAMPLE:
10 OPEN #1,4,0,"D:TEST"
20 TRAP 60:REM GOES TO LINE 60 WHEN END OF FILE ERROR OCCURS
30 GET #1,IN
40 IN$(LEN(IN$)+1)=CHR$(IN)
50 GOTO 30
60 CLOSE #1
In assembly language, the get command can be used to get any number of
bytes from the device. It works just as INPUT does except EOLs are
ignored.
IOCB get-byte parameters:
ICCOM get-character (single byte) code
ICBAL \
ICBAH same as in input
ICBLL
ICBAH /
Other than the ICCOM code (GETCHR = $07) this command is identical to
the input command.
PUT: (ICCOM = $0B)
In BASIC, PUT is the opposite of GET. It outputs a single byte from a
variable to the device. PUT is used the same as GET. For example:
PUT #1,OUT
In assembly language, the command byte of the IOCB is loaded with the
put-character code (PUTCHR = $0B). Otherwise the PUT command is
identical to GET.
CLOSING A CHANNEL
Closing a channel frees it for use by another device or for changing
parameters. In assembly language the close code is put into the
command byte of the IOCB then the CIOV call is made.
IOCB close command:
CLOSE = $0C
:
LDX IOCB1
LDA CLOSE
STA ICCOM,X
JSR CIOV
In BASIC, use the CLOSE command followed by the channel number.
CLOSE #1
With the disk drive, the file name is not put into the directory until
the channel is closed.
THE DEVICE TABLE
CIO uses a jump table located at $031A (794). When a CIO call is
made, CIO searches the table for the one-byte device name. The two
bytes following the device name contain the address of the device
handler's vector table. CIO searches the device table from the end,
$033D (829) to the beginning. This way, if a custom handler has ben
substituted for a resident handler, the custom handler will be found
first. (custom handlers cannot be inserted directly in the place of
resident handlers in the device table.)
Each handler has its' own vector table. This vector table is 16 bytes
long. The two-byte vectors point to the various handler routines.
The vectors are stored in the vector table in the following order:
Handler vector table order
open
close
get byte
put byte
get stat
special
JMP init code (3 bytes)
The open routine should validate the ICAX parameters and check for
illegal commands.
The close routine should send any remaining data in the buffer to the
device, mark the End-Of-File and update any directories, etc.
The get byte routine should get a byte from the device or the handler
buffer and put it in the 6502 A register. Handlers with long timouts
must monitor the break key flag and put a $80 in the 6502 Y register
if the [BREAK] key is pressed.
The put byte routine should send the byte in the 6502 A register to
the device or handler buffer. If the buffer fills, it should be sent
to the device. BASIC can call the put byte routine without using
CIO.
The get status routine may get 4 bytes of status information from the
device and put them in DVSTAT [$02EA] to DVSTAT+3.
For special commands the handler must examine the command byte and
find the proper routine entry point.
In all cases the status (error code) of the operation should be put in
the 6502 Y register.
To be compatible with all versions of the operating system, the
handler must redirect DOSINI [$000C,2 (12)] for initialization upon
reset. This initialization must restore the vectors in the handler
vector table and jump to the origional DOSINI vector.
SPECIAL COMMANDS
Some devices have special CIO commands. These are known as device
specific commands. In assembly language these commands are executed
just as any other CIO command is. In BASIC the XIO command is used.
An example of the XIO command is:
XIO command code #channel,aux1,aux2,device:file name
To open a channel with the XIO command instead of the OPEN command
use:
XIO 3 #1,4,0,"K:"
Note that the above command is identical to the OPEN command except
"XIO 3" is used instead of "OPEN". Also note that $03 is the IOCB
open code for ICCOM.
Useful database variables and OS equates
DOSINI $000C,2 (12): initialization vector
BRKKEY $0011 (17): break key flag
ICHID $0340 (832): start of IOCBs
ICDNO $0341 (833):
ICCOM $0342 (834):
ICSTA $0343 (835):
ICBAL $0344 (836):
ICBAH $0345 (837):
ICPTL $0346 (838):
ICPTH $0347 (839):
ICBLL $0348 (840):
ICBLH $0349 (841):
ICAX1 $034A (842):
ICAX2 $034B (843):
HATABS $031A,16 (794): device handler table
CIOV $E456 (58454): CIO entry vector
CHAPTER 2
THE DISK OPERATING SYSTEM (D:)
The disk operating system program (DOS) is also called the file
management system (FMS). DOS is not a permanent part of the computer,
it is loaded in upon power-up if a disk drive is attached to the
computer.
When the computer is turned on, one of the first things it does is
send a request to the disk drive to load DOS into the computer. This
startup operation is called booting. The word boot is short for
bootstrapping -- the start-up process of early computers. The term
comes from "lifting one's self by one's boot straps".
Anytime the disk boots, the computer tries to read a program starting
at sector 1 and continuing in sequence. If the disk has DOS on it,
the first three sectors, called the boot record, have a program which
loads the DOS.SYS file. If there is no DOS.SYS file on the disk the
computer will display:
--------------------
| BOOT ERROR |
| BOOT ERROR |
| BOOT ERROR |
| BOOT ERROR |
| BOOT ERROR |
| BOOT ERROR |
| (etc.) |
| |
| |
--------------------
When a disk is formatted, the drive read/write head passes over the
entire disk and puts magnetic marks on it. These marks divide the
disk into 32 concentric tracks. With DOS 2.0 each track is divided
into 18 sectors, each holding 128 bytes of data. With DOS 2.5 there
are 32 sectors per track giving a total of 1,024 sectors.
Each sector on the disk is marked with a reference number from 1 to
720. Unfortunately, the writers of DOS 2.0 didn't know this so they
wrote the DOS to use sectors numbered from 0 to 719. As a result, DOS
2.0 cannot access sector 720. The designers of the disk drive were
the guilty party in this case. It is normal to number from 0 in
computers. With DOS 2.5, sectors 720 - 1,024 can be accessed
normally.
Sector 720 can be accessed using the computer's resident disk handler.
Some software writers use sector 720 to hide special information to
make their programs difficult to copy.
DOS 2 SECTOR ASSIGNMENTS
Sectors 1 through 3 are called the boot record. They contain a
program which loads the DOS.SYS file into memory.
Sector 360 is called the Volume Table of Contents or VTOC. The main
purpose of the VTOC is to keep track of what sectors are occupied.
Bytes 3 and 4 of the VTOC tell how many sectors are available.
Starting at byte 10 is the Volume Bit Map. Each byte in the VBM tells
the status of eight sectors. If a bit is a 1 the sector is available.
If a bit is a 0 the sector is occupied.
Sectors 361 through 368 contain the disk directory. Each directory
sector holds eight file names. The first byte of a file name is
called the flag byte. It tells the status of that file.
Directory flag byte.
7 6 5 4 3 2 1 0
-----------------
| flag byte |
-----------------
Bits: 7 1 = file deleted
6 1 = file in use
5 1 = file locked
0 1 = open for output
The next two bytes tell how many sectors are in the file. The two
bytes after them tell the starting sector of the file. The last 11
bytes contain the file name.
Sector 720 cannot be accessed with DOS 2.0.
The boot record, VTOC, directory and sector 720 use 13 sectors. This
leaves 707 sectors for storing files with DOS 2.0.
Each file sector has 125 bytes of data. The last three bytes tell how
many bytes of the sector are used, what directory entry the sector
belongs to and which sector is next in the file.
File sector structure
7 6 5 4 3 2 1 0
-----------------
| data | byte 0
- - - -
| bytes | byte 124
-----------------
| Dir. No. |hi | byte 125
-----------------
|forward pointer| byte 126
-----------------
|S| byte count | byte 127
-----------------
hi = high 2 bits of forward pointer
S = Short sector flag. 1 = short sector (End Of File)
If the directory number does not match the order of the file name in
the directory, an error 167 (file number mismatch) will occur.
As a file is written to an empty disk it is put in consecutive
sectors, 125 bytes at a time. After the file is written, the VTOC and
directory are updated. When new files are written they also use
consecutive sectors.
When a file is deleted the status bit of the directory is changed to
show that the file has been deleted. DOS then tracks the file, sector
by sector, to find what sectors are used. Finally the VTOC is updated
to show that the deleted file's sectors are available for new files.
The file is not erased from the disk; only the VTOC and directory are
changed.
When a file is deleted, an "island" of free sectors may be left on the
disk. When a new file is then written to the disk it will first use
these new free sectors. When the island is used up, DOS will skip
over the occupied sectors to the next free sector. This is the reason
for the sector link. A file can end up with it's sectors scattered
all over a disk. It can be complicated but it's efficient.
DISK FILE STRUCTURE
The first few bytes of a file may tell DOS or another program what
kind of file it is. These information bytes are called a header.
A text file is any file which has no header. A listed BASIC program
is a type of text file. A letter from a word processor is another.
A binary load file is a file intended to load to a specific address in
memory. The first two bytes of a binary load file are decimal 255.
The next two bytes hold the address at which the file is to load. The
last two header bytes tell the ending address for the file. If the
file is a program and is to run automatically, the initialization and
run address are appended to the end of the file.
binary load file header
Decimal Hexadecimal
255 identifier FF
255 FF
0 start 00
7 07
15 end FF
8 08
The above file would load at address $0700 (1792 decimal) and end at
address $08FF (2063). If a binary load file has initialization and
run address appended to it they take on the following format:
Init and run tailer
CHR Decimal Hexadecimal
init address format
[b] 226 identifier E2
| 2 02
[c] 227 E3
| 2 02
n address nn
n nn
run address format
[diamond] 224 identifier E0
| 2 02
[a] 225 E1
| 2 02
n address nn
n nn
[ ]=inverse video
A program which doesn't need special initialization can be run at the
init address. Otherwise, an RTS instruction is expected at the end of
the initialization section. The computer will then jump to the run
address if specified.
INSIDE THE COMPUTER
DOS uses the computer's CIO utility. When a DOS disk is booted a
non-resident handler is loaded into memory. A new handler name, D, is
then added to the handler table. When CIO is called with a device
name of D: or Dn:, CIO will search the handler table for that device
name. If the 'D' is found, the next two bytes in the table point to
the DOS entry address.
DOS FILE NAME CONVENTIONS
DOS is unique among CIO handlers in that it requires an eight
character file name to follow the device name. This file name may be
followed by a period and then a three character extender.
EXAMPLES: D:TEST, D2:FIREMAN, D:VENTURE.EXE, D:CHAPTER.001
The D2: is used for drive number two if present.
The file name must use upper-case letters or numbers. The first
character must always be a letter.
WILD CARDS
The characters * and ? may be used as wild cards. * means any
combination of characters and ? means any single character.
EXAMPLES: D:P* any file beginning with P and
without an extender
D:*.EXE any file with the extender .EXE
D:*.* any file.
D:F?REMAN one unknown character,
FIREMAN or FOREMAN will match
Wild cards can only be used to load, delete, lock and unlock files.
When loading a file using wild cards, only the first matching file
will be loaded.
When renaming a file, both the new and old names are expected after
the device name.
EXAMPLE: D:OLDNAME.BAS,NEWNAME.BAS
To format a disk, only the device name (D: or Dn:) is needed.
USING DOS
When a CIO channel is opened to the disk drive it must actually be
opened to a specific file on the disk. The device name in the open
command must be followed by a file name.
When a channel is opened to the disk, two special parameters may be
used in ICAX1.
ICAX1 for disk open:
7 6 5 4 3 2 1 0
-----------------
| W R D A|
-----------------
D 1 = open to read the directory instead of a file
A 1 = append data to the end of the file
This gives the following extra ICAX1 options.
Disk specific ICAX1 options:
HEX DEC
$06 6 open to read directory
$09 9 output, append to the end of an
existing file
READING THE DIRECTORY
When the directory is read, each file name is treated as if it were
followed by an EOL. A loop must be used to read all of the file names
in the directory. The last entry read is the free sector count.
After it is read, another read operation will result in an End-Of-File
error.
The disk drive has a number of device specific commands other than the
regular CIO commands. From BASIC the XIO command is used to access
these commands. The XIO command allows you to directly load the IOCBs
from BASIC. Each parameter of the XIO command places values in
certain bytes of an IOCB.
XIO command format:
XIO command channel,aux1,aux2,device:file name
Note that the parameters resemble the BASIC OPEN command. The BASIC
OPEN command is identical to it's equivalent XIO command.
XIO commands specific to the disk drive.
RENAME XIO $20 (32)
DELETE XIO $21 (33)
LOCK XIO $23 (35)
UNLOCK XIO $24 (36)
POINT XIO $25 (37)
NOTE XIO $26 (38)
FORMAT XIO $FE (254)
EXAMPLES:
XIO 33 #1,0,0,"D:JUNK" = delete file named D:JUNK
XIO 32 #1,0,0,"D:OLD,NEW" = change name of D:OLD to D:NEW
NOTE and POINT can also be used directly from BASIC. NOTE finds the
current position of the read/write head on the disk. POINT moves the
read/write head to the desired position.
USING NOTE AND POINT
The command format for NOTE and POINT is as follows:
NOTE \
channel,sector,byte
POINT/
EXAMPLE:
NOTE #1,SECT,BYTE
BASIC requires the sector and byte parameters in both commands to be
variables. Fixed numbers cannot be used. If you try to do a POINT to
a sector outside the file the channel is open to, a point error will
occur. Care may need to be taken to be sure the file being accessed
is in contiguous sectors on the disk. If it is not, it will be
difficult to know where to do points to.
One use of NOTE is to use the command immediately after opening a
channel to a disk file. After the NOTE command, the parameter
variables contain the coordinates of the first byte of the file. They
can then be used as a reference for the POINT command.
In assembly language, ICAX3 and ICAX4 are used for the sector number
(lsb,msb). ICAX5 is used for the byte number.
STATUS REQUEST
If the status request command is used, one of the following values
will be found in ICSTA and the 6502 Y register.
HEX DEC
$01 1 OK
$A7 167 file locked
$AA 170 file not found
CHAPTER 3
USING THE DOS 2 UTILITIES (DUP.SYS)
If you boot a DOS disk with no cartridge in the slot or with BASIC
disabled (by holding the OPTION key), DOS will try to load the file
named DUP.SYS. This is the disk utility file. When using BASIC,
typing DOS [RETURN] will load the DUP.SYS file. When the utilities
are loaded the menu will appear on the screen.
THE DOS UTILITIES MENU
DISK OPERATING SYSTEM II VERSION 2.0S
COPYRIGHT 1980 ATARI
A. DISK DIRECTORY I. FORMAT DISK
B. RUN CARTRIDGE J. DUPLICATE DISK
C. COPY FILE K. BINARY SAVE
D. DELETE FILE(S) L. BINARY LOAD
E. RENAME FILE M. RUN AT ADDRESS
F. LOCK FILE N. CREATE MEM.SAV
G. UNLOCK FILE O. DUPLICATE DISK
H. WRITE DOS FILES
SELECT ITEM OR [RETURN] FOR MENU
[A] DIRECTORY
After pressing [A] [RETURN] you will get the prompt:
DIRECTORY--SEARCH SPEC,LIST FILE?
If you want to see the entire directory just press [RETURN] again. If
you wish, you may type in a specific file name (D: is optional) or
wild cards to search for. If you specify a search spec only matching
files will be displayed.
If you want, you can have the directory sent to another device. To do
this type a comma and the device name. For example, if you type ,P:
the directory will be sent to the printer.
[B] RUN CARTRIDGE
If a cartridge was inserted or BASIC was not disabled when the
computer was turned on, [B] [RETURN] will run that cartridge or
BASIC.
[C] COPY FILE
This option will copy a file to another part of the same disk (with a
different file name) or copy from one disk drive to another. When you
press [C] [RETURN] you will be given the prompt:
COPY--FROM,TO
Type the devices and file names separated by a comma.
EXAMPLES:
FOREMAN,FIREMAN
or
D1:TEST,D2:TEST
The first example will copy to the same disk. The second example will
copy from disk drive one to disk drive two.
If you want to have the first file appended to the end of the second
file type /A after the file names.
EXAMPLE:
RUNMENU.EXE,AUTORUN.SYS/A
If the files are binary load files, this will cause both files to be
saved as one file. When the load command is used they will both be
loaded and run.
[D] DELETE FILE(S)
After pressing [D] [RETURN] you will get the prompt:
DELETE FILE SPEC
After typing the file name you will be asked to confirm the file to
delete.
DELETE FILE SPEC
DELETE-D1:JUNK ARE YOU SURE?
Press [Y] if the correct file is displayed. If you use wild cards you
will be asked to confirm each matching file.
[E] RENAME
Upon typing [E] [RETURN] you will be given the prompt:
RENAME-GIVE OLD NAME,NEW
Type the file name you want to change and the new name separated by a
comma.
EXAMPLE:
COLT,HORSE
WARNING! Do not rename a file to a name which already exists on the
disk. You will end up with a duplicate file name and will not be able
to access one of them. Attempting to rename or delete one of them
will rename or delete both. The only way to fix a duplicate file name
is with a sector editor or other special utility.
[F] LOCK FILE
A locked file cannot be written to, renamed or deleted. To lock a
file type [F] [RETURN]. You will get the prompt:
WHAT FILE TO LOCK?
Type the file name you want to lock. Wild cards will cause all
matching files to be locked.
[G] UNLOCK FILE
Used the same as lock.
[H] WRITE DOS FILES
This option will write the DOS.SYS and DUP.SYS files to a formatted
disk. When you type [H] [RETURN] you will receive the prompt:
DRIVE TO WRITE DOS FILES TO?
Type the number of the drive. If the drive contains a formatted disk
the dos files will be written to it.
[I] FORMAT DISK
This option formats a new disk or erases a disk with files on it.
Typing [I] [RETURN] will get you the prompt:
WHICH DRIVE TO FORMAT
Be sure you have the correct disk in the proper drive then type the
drive number. It is impossible to recover files on a disk formatted
by accident.
While the disk is being formatted the drive will check to be sure the
disk is formatted correctly. If not, the drive attempt to format the
disk again. If the disk is defective the drive will not finish the
formatting process.
[J] DUPLICATE DISK
This option will copy an entire disk except for sectors listed as free
in the VTOC. Some programs are copy-proofed by changing the VTOC to
show that some occupied sectors are empty. For such disks, a program
which copies the entire disk is needed.
When you press [J] [RETURN] you will be given the prompt:
DUP DISK--SOURCE,DEST DRIVES?
If you are using only one disk drive, type 1,1. If you have only one
drive you will be told when to swap disks.
[K] BINARY SAVE
This option saves a block of memory as a binary load file. When you
type [K] [RETURN] you will be given the prompt:
SAVE-GIVE FILE,START,END(,INIT,RUN)
Type the desired file name and a comma. Now type the start and end
addresses of the memory block to be saved, in hexadecimal numbers,
separated by commas. If the file is a program which is to
automatically run when loaded, give the initialization address, if
needed, then the run address.
EXAMPLE:
CHASE.EXE,0700,09FF,,0700
This will save the block of memory from address 0700 to 09FF. The
program is not initialized before running so there is no address typed
after the third comma. When the program is loaded the computer will
jump to address 0700, as specified in the last parameter, to run the
program.
[L] BINARY LOAD
To load a binary file type [L] [RETURN]. You will get the Prompt:
LOAD FROM WHAT FILE?
Type the file name and the file will be loaded. If wild cards are
used, only the first matching file will be loaded.
[M] RUN AT ADDRESS
Typing [M] [RETURN] will get the prompt:
RUN FROM WHAT ADDRESS?
Type the hexadecimal address of the program you want to run.
[N] CREATE MEM.SAV
A MEM.SAV file is used by BASIC and some other programs to save the
part of memory which the DUP.SYS file loads into. If there is no
MEM.SAV file on the disk when you go to the DOS utilities, you will
loose that part of memory. With BASIC you will loose your program.
When you type [N] [RETURN] you will get the prompt:
TYPE Y TO CREATE MEM.SAV
Typing [Y] [RETURN] will create a MEM.SAV file on the disk in drive
one.
[O] DUPLICATE FILE
This option is used to copy a file from one disk to another, using
only one disk drive. When you type [O] [RETURN] you will get the
prompt:
NAME OF FILE TO MOVE?
If you use wild cards you will be asked to swap disks for each
matching file.
DOS 2.5 also has option:
[P] FORMAT SINGLE
DOS 2.5 normally formats disks to use "enhanced" density. This option
will format a disk in single density for use with the 810 drive.
DOS 2.5 also has some special utilities on the master disk. Use the
binary load option to run them.
RAMDISK.SYS
This program will cause the extra bank of memory in the 130XE to act
like a disk drive (called D8:). If this program is on the disk it
will automatically run. It need not be renamed to AUTORUN.SYS.
COPY32.COM
Copies DOS 3 files to DOS 2.
DISKFIX.COM
Can make certain "repairs" to a disk, such as restoring deleted
files.
SETUP.COM
Used to change the default configuration of DOS.
AUTORUN.SYS (DOS 2.0 and 2.5)
This program is needed to operate the RS-232 ports on the 850
interface. If you don't want this program to automatically load when
you boot with the master disk, rename the file to RS232.
SPECIAL DOS INFORMATION
When DOS is in memory, changes can be made to the DOS program. These
changes can be made by poking the changes into memory. If you want to
make the changes permanent, you can type DOS [RETURN] to load the
utilities. From the utilities menu you can use the write DOS files
option to save the changes on disk. Some of the useful changes you
can make follow.
POKE 1913,80
This turns off the write verify and speeds up disk writing.
POKE 1913,87
This turns write verify on
POKE 5903,42
POKE 5904,46
POKE 5905,82
POKE 5906,85
POKE 5907,78
POKE 5908,155
This causes any binary file with the extender .RUN to be loaded
automatically when the computer is turned on.
POKE 5903,65
POKE 5904,85
POKE 5905,84
POKE 5906,79
POKE 5907,82
POKE 5908,85
This returns the DOS to normal, Automatically loading files named
AUTORUN.SYS.
DOS 2.0 DOS 2.5
POKE 3772,255
POKE 3818,64 POKE 3774,64
POKE 3822,123 POKE 3778,123
This will cause DOS to accept lower-case as well as upper-case letters
in file names. It will also now accept @,[,\,],^ and _ .
POKE 3772,223
POKE 3818,65 POKE 3774,65
POKE 3822,91 POKE 3778,91
This will change DOS back to normal, accepting only upper-case letters
and numbers.
CHAPTER 4
THE CASSETTE HANDLER (C:)
The cassette handler sends data to the cassette recorder in blocks of
128 bytes each. The blocks are sent in the following format:
Cassette record format
-----------------
|0 1 0 1 0 1 0 1| speed measurement bytes
-----------------
|0 1 0 1 0 1 0 1|
-----------------
| control byte |
-----------------
| 128 |
= data =
| bytes |
-----------------
| checksum | handled by SIO
-----------------
The control byte may have one of the following values.
$FC (252) record is full.
$FA (250) partly full, next record is EOF.
$FE (254) EOF record, data section is all zeroes.
The cassette handler has two modes of operation. The first mode uses
only a short gap between records. It is called the no IRG
(interrecord gaps) mode. The second mode uses longer gaps between
records and is called the IRG mode. In the IRG mode the computer may
stop the cassette recorder between records for processing data.
When a channel is opened to the cassette recorder, bit 7 of ICAUX2 may
be set to 1 (ICAX2 = $80 (128)). This will cause the cassette to use
the no IRG mode.
A cassette file starts with a 20 second mark tone. This tone is
followed by the file records with 128 data bytes each. The final
record is an End-Of-File record.
The cassette is a straight-forward read/write device. There are no
special functions other than those common to other CIO devices.
The cassette motor is controlled by one of the controller port control
registers. If bit 3 of PACTL [$D302 (54018)] is 0 then the cassette
motor is on. The following BASIC commands will turn the cassette
motor on and off.
Cassette motor control.
POKE 54018,PEEK(54018)-8 motor on
POKE 54018,PEEK(54018)+8 motor off
Useful data base variables and OS equates
PACTL $D302 (54018): port A control register, bit 4
controls cassette motor
CHAPTER 5
THE KEYBOARD HANDLER (K:)
The keyboard is a read only device and therefore the keyboard handler
has no output functions.
The keyboard handler reads the keys as ATASCII codes. Each key is
represented by one byte of data. Therefore, each time a key is
pressed the data is treated as a byte of data just as data from any
other device is. The only difference is that the computer must wait
for the operator to press the keys as it reads the data.
Whenever a key is pressed an IRQ interrupt is generated by the
keyboard reading hardware. The internal code (not ATASCII) for the
key just pressed is then stored in CH [$02FC (764)]. The code is then
compared with the prior key code in CH1 [$02F2 (754)]. If the code in
CH1 is different from the code in CH, the key is accepted. The code
is then converted to ATASCII, and placed in the database variable
ATACHR [$02FB (763)]. On XL and XE models, KEYDEF [$0079,2 (121)]
points to the key-code-to-ATASCII conversion table. (This address is
used by the the screen handler in 400/800 models).
If the code in CH1 is the same as the code in CH, the new key code
will not be accepted unless the key debounce timer, KEYDEL [$02F1
(753)] is 0.
When CIO is told to do an input operation from the keyboard, CH is
checked to see if a key has been pressed. If CIO finds $FF (255) in
CH, it waits until a key is pressed. If CH is not $FF, a key has been
pressed and the ATASCII code for that key is taken from ATACHR. CH is
then set to $FF.
The data in CH is in the following format.
Key code format:
7 6 5 4 3 2 1 0
-----------------
|C|S| key code |
-----------------
C 1 = [CTRL] key is pressed
S 1 = [SHIFT] key is pressed
Anytime a key is pressed, CH is loaded with the key code. CH will
hold the code until the computer is commanded to read the keyboard.
Sometimes the computer will read a key which was pressed long ago. If
you want to prevent this, load CH with $FF before reading the
keyboard. (In BASIC use POKE 764,255.) This will clear out any old
key pressings.
Special function keys
[CTRL][1] screen output start/stop
[CTRL][2] BELL
[CTRL][3] Generates End-Of-File status
[/|\]
or
[/] inverse video toggle
[CAPS LOWER] sets lower case
[CTRL][CAPS] sets CTRL lock
[SHIFT][CAPS] sets caps lock
KEYBOARD REPEAT DELAY AND RATE CONTROL
On the XL and XE, KRPDEL [$02D9 (729)] determines the delay before the
key repeat begins. The value of this byte is the number of vertical
blanks (1/60th second each) to delay. KEYREP [$02DA (730)] determines
the repeat rate in vertical blanks.
KEYBOARD CLICK
The keyboard click of the XL/XE is heard through the TV speaker. The
click may be turned off by putting $FF in NOCLIK [$02DB (731)].
NON-HANDLER, NON-CIO KEYS
The [OPTION], [SELECT] and [START] keys are read from the console
switch register, CONSOL [$D01F (53279)].
The console switch register
7 6 5 4 3 2 1 0
-------------------------
CONSOL |0 |0 |0 |0 |SP|OP|SE|ST|
-------------------------
8 4 2 1
ST 0 = [START]
SE 0 = [SELECT]
OP 0 = [OPTION]
SP Console speaker. set to 1 during vertical blank.
toggleing this bit operates the speaker (which
is heard through the TV on XL/XE models).
This bit always reads 0
The [HELP] key on XL and XE models is read from HELPFG, [$02DC (732)].
This address is latched and must be reset to zero after being read.
The [HELP] key register
7 6 5 4 3 2 1 0
-----------------
HELPFG |C S 0 H 0 0 0 H|
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
H 1 = [HELP] (bits 0 and 4)
S 1 = [SHIFT]
C 1 = [CONTROL]
Useful database variables and OS equates
KEYDEF $0079,2 (121): key code coversion table vector (XL/XE)
KRPDEL $02D9 (729): delay before key repeat (XL/XE)
KEYREP $02DA (730): key repeat rate (XL/XE)
NOCLIK $02DB (731): $FF turns off key click (XL/XE)
HELPFG $02DC (732): [HELP] key (XL/XE)
ATACHR $02FB (763): ATASCII Code for last key
CH $02FC (764): keycode, $FF if no key has been pressed
BRKKEY $0011 (17): break key flag, 0 = break key pressed
SRTIMR $022B (555): Key delay and repeat timer
SHFLOK $02BE (702): SHIFT/CTRL lock flag
$00 = lower case
$40 (64) = upper case lock
$80 (128) = CTRL lock
INVFLG $02B6 (694): inverse video flag, non-zero = inverse
CONSOL $D01F (53279): start, select and option keys
IRQEN $D20E (53774): IRQ interrupt enable
bit 7 enables [BREAK]
bit 6 enables other keys
shadow registers
POKMSK $0010 (16): IRQEN shadow
CHAPTER 6
THE PRINTER HANDLER (P:)
The printer is a write only device so the printer handler has no input
functions. The printer handler has no special functions other than
the CIO functions common to all other devices.
Although many printers have special functions, the printer handler has
no control over them. See your printer manual for information on
special functions.
CHAPTER 7
SCREEN EDITOR (E:)
The screen editor uses both the keyboard handler and the screen
handler to provide interactive control of the computer. In fact, the
keyboard handler, the screen handler and the screen editor are
contained in a single section of code and are therefore very closely
related.
The editor works with one line of characters at a time. The lines it
works with are called logical lines and are up to three screen lines
long.
The screen editor inputs data from the keyboard and then prints the
data on the screen. When the [RETURN] key is pressed, the editor
inputs all of the data on the present logical line for processing by
CIO.
If characters are typed on the screen, and then the cursor is moved
off the line, then back on the line, and new characters are typed,
only the characters to the right of the reentry point of the cursor
are input when [RETURN] is pressed. However, if the cursor is moved
off the line again, then moved back on, all characters on that logical
line are input.
If bit 0 of ICAX1 is 1, the editor will act as if the [RETURN] key is
being held down. This bit may be changed at any time.
Editor control codes
The screen editor treats certain ATASCII codes as special control
codes.
Screen editor control codes
KEY HEX DEC FUNCTION
[RETURN] $9B 155 carriage return or EOL
[CLEAR] $7D 125 Clear screen,put cursor in upper left
[UP ARROW] $1C 28 Move cursor up one screen line
[DOWN] $1D 29 down one line
[LEFT] $1E 30 left one character
[RIGHT] $1F 31 right one character
[BACK S] $7E 126 Back-space operation
[SET TAB] $9F 159 sets tab stop at cursor
[CLEAR
TAB] $9E 158 Clear tab stop at cursor
[TAB] $7F 127 move to next tab stop
[SHIFT]
[INSERT] $9D 157 Make space for a new line
[SHIFT]
[DELETE] $9C 156 delete the logical line at the cursor
[CTRL]
[INSERT] $FF 255 make room for a character
[CTRL]
[DELETE] $FE 254 delete character at cursor
[ESCAPE] $1B 27 causes next non-EOL code to be
displayed as an ATASCII character, even if it is an editor
control code
[CTRL][1] screen print start/stop
[CTRL] $FD
CHAPTER 8
THE DISPLAY HANDLER (S:)
The display handler manages the computer's video display. Although no
data ever leaves the computer through it, the display is treated like
any other CIO device. Data sent to the screen may be displayed as
either characters or point by point graphics. Although it is only
visible in the 40 column text mode, mode 0, there is a cursor on the
screen in all of the text or graphics modes. Whenever a character or
graphics point is put on the screen, the cursor moves just as in mode
0.
The display is capable of both input and output. Information can be
put on the screen with any of the CIO output commands. An input
command will find whatever is on the screen at the position of the
cursor.
When text or graphics is sent to the screen it is actually stored in
an area of memory called the display buffer. What you see on the
screen is the computer's interpretation of the data stored there.
This will be explained further as each mode is covered.
DISPLAY HANDLER SPECIAL FUNCTIONS:
DRAW
FILL
SPECIAL ERROR STATUSES:
$84 (132) Invalid special command.
$8D (141) Cursor out of range.
$91 (145) Nonexistant screen mode.
$93 (147) Insufficient ram for screen mode.
TEXT MODE 0
In graphics mode 0, data passes through CIO, and is stored in the
display buffer in the following format.
7 6 5 4 3 2 1 0
-----------------
|I| Data |
-----------------
I 1 = displays character in inverse video.
Bits 0 through 6 select one of the 128 characters in the ATASCII set.
If bit seven = 1, the character is displayed in inverse video.
Converting the above byte to decimal will give the BASIC ASC(x)
equivalent.
The characters displayed in the text modes are determined by tHE
ATASCII character set. This is a bit by bit representation of how the
characters appear on the screen. The character set starts $E000
(57344) in the operating system ROM. From there, for 1K of memory,
each eight bytes holds a "bit map" of a particular character. Below
is how the letter A is stored in the character set.
Letter A as represented in the C-set
7 6 5 4 3 2 1 0
-----------------
$E208 |0 0 0 0 0 0 0 0|
-----------------
|0 0 0 1 1 0 0 0| * *
-----------------
|0 0 1 1 1 1 0 0| * * * *
-----------------
|0 1 1 0 0 1 1 0| * * * *
-----------------
|0 1 1 0 0 1 1 0| * * * *
-----------------
|0 1 1 1 1 1 1 0| * * * * * *
-----------------
|0 1 1 0 0 1 1 0| * * * *
-----------------
$E20F |0 0 0 0 0 0 0 0|
-----------------
XL and XE models have an international character set starting at $CC00
(55224). In this character set the graphics characters are replaced
by international characters.
Custom characters sets may be loaded at any free address which is a
multiple of 1,024 ($0400, or 1K). The database variable CHBAS [$02F4
(756)] stores the most significant byte (MSB) of the address of the
active C-set. Since the LSB of the C-set address is always $00, no
LSB is needed to find it.
The data stored in the display buffer does not use the ATASCII code.
A special code needed by the ANTIC chip is used.
DISPLAY CODE / ATASCII CODE CONVERSION:
ATASCII display
$00 - $1F ( 0 - 31) = $40 - $5F (64 - 95)
$20 - $5F (32 - 95) = $00 - $3F ( 0 - 63)
$60 - $7F (96 - 127) = unchanged
The codes for inverse video (the above codes with bit 7 set (= 1) or
the above codes + 128 in decimal) are treated likewise.
When you first turn on the computer, BASIC opens channel 0 to the
screen editor (E:). The screen editor uses both the keyboard handler
and the screen handler, in mode 0, to display characters when they are
typed in.
TEXT MODES 1 AND 2
Graphics modes 1 and 2 offer a split screen configuration if desired.
The split screen has four lines of mode 0 at the bottom of the
screen.
In mode 1 the screen holds 20 characters horizontally and 24
characters vertically. In mode 2 the characters are twice as tall so
the screen holds 12 vertically.
In BASIC, characters are sent to the screen with the PRINT command.
Since BASIC uses channel 6 for graphics you must specify channel 6 in
the command. For example:
? #6;"HELLO"
If you use a comma in place of the semicolon, ten spaces will print
before the "HELLO"
You can also use the PLOT and DRAWTO commands. In this case the COLOR
command determines the character, as well as the color to be
displayed.
Data passes through CIO in the following form:
7 6 5 4 3 2 1 0
-----------------
| C | D |
-----------------
C determines the color.
C Default Color Shadow
Color Register Register
0 green COLPF1 COLOR1
1 gold COLPF0 COLOR0
2 gold COLPF0 COLOR0
3 green COLPF1 COLOR1
4 red COLPF3 COLOR3
5 blue COLPF2 COLOR2
6 blue COLPF2 COLOR2
7 red COLPF3 COLOR3
D is a 5 bit ATASCII code which selects the character to be displayed.
The database variable CHBAS selects between upper case (CHBAS=$E0
(224)) and lower case (CHBAS=$E2 (226)).
GRAPHICS MODES 3 THROUGH 11
Modes 3 through 8 offer a split screen mode. In modes 9 through 11
special programming is required for split screens.
These modes use dot by dot (pixel by pixel) graphics instead of
character sets. Before explaining how graphics are sent to the screen
through CIO, I will describe how the data in the display buffer is
interpreted by the ANTIC chip.
Mode 8 is the simplest of the graphics modes. Each byte of the
display buffer controls eight pixels horizontally. The first 40 bytes
of the display buffer control the first horizontal line of graphics.
This makes a total of 320 pixels horizontally. If one of the eight
bits of a byte is a 1 then the pixel it controls is on. If a bit is a
0 then it's pixel is off. For example, if a particular byte is equal
to $9B (binary 10011011) then its' part of the screen would look
like...
* ** **
(10011011)
In reality the pixels are assigned to different color registers. A
color register is a byte of memory which controls the color of all
pixels assigned to it. In mode 8, if a bit is = 0 it's pixel is
assigned to the register called COLBK. If a bit is one, it's pixel is
assigned to COLPF0. See COLORS below for more information on the
color registers.
You may notice a close similarity between mode 0 and mode 8. The
major difference between these modes is where the dot by dot
information comes from. In mode 8 this information comes from the
display buffer. In mode 0 the display buffer contains codes telling
what characters to display. The actual dot by dot information comes
for the character set at $E000.
In mode 7 each pixel is controlled by two bits. Therefore each byte
only controls four pixels. There are also only 1/4 as many pixels on
the screen as in mode 8. See mode 3 below for an explanation of how
the each byte affects the pixels.
In a graphics mode, when CIO sends a byte of data to the screen
handler, that byte has information for only one pixel. Do not confuse
a byte which CIO sends to the screen handler with the bytes in the
display buffer.
CIO sends data to or retrieves data from the screen in the following
forms.
7 6 5 4 3 2 1 0
-----------------
|0 0 0 0 0 0| D | Modes 3,5,7 -- D = color
-----------------
-----------------
|0 0 0 0 0 0 0|D| Modes 4,6,8 -- D = Color
-----------------
-----------------
|0 0 0 0| D | Modes 9,10,11 -- D = data
-----------------
Mode 3 uses a screen which is 40 pixels horizontally and 24
vertically. Each pixel is a square the size of a mode 0 character.
It requires 273 bytes of RAM where each byte controls 4 pixels. Each
pair of bits controls which of the four color registers their pixel is
assigned to.
display buffer byte for mode 3
7 6 5 4 3 2 1 0
-----------------
| D | D | D | D |
-----------------
P1 P2 P3 P4
Pixel/color register assignments:
D = 00 COLBK (COLOR4)
01 COLPF0 (COLOR0)
10 COLPF1 (COLOR1)
11 COLPF2 (COLOR2)
Mode 4 uses a screen of 80 columns by 48 rows. Each pixel is half the
size of those in mode 3. Mode 4 requires 537 bytes of RAM where each
byte controls 8 pixels. This mode is very similar to mode 8 except
there are fewer but larger pixels.
Mode 5 uses a screen of 80 columns by 48 rows. The pixels are the
same size as in mode 4. Mode 5 requires 1,017 bytes of RAM where each
byte controls 4 pixels in the same manner as in mode 3.
Mode 6 uses a screen of 160 columns by 96 rows. It requires 2,025
bytes of RAM where each byte controls 8 pixels as in mode 4.
Mode 7 uses a screen of 160 columns by 96 rows. It requires 3,945
bytes of RAM where each byte controls 4 pixels as in modes 3 and 5.
Modes 8 through 11 (and 15 on XL and XE models) each require 7,900
bytes of RAM and are very similar in display set up. The main
differences between these modes is the interpretation of data in the
display buffer.
Mode 15 (sometimes called mode 7.5) uses a screen of 160 columns by
192 rows. Each byte controls 4 pixels as in mode 7. The main
difference between mode 15 and its related modes is bit 0 of each
instruction byte in the display list (the program which the ANTIC chip
uses). If this bit is 0 the screen is interpreted as mode 15. If the
bit is 1 the screen is interpreted as modes 8 through 11.
Modes 8 through 11 are set up identically in memory, including the
display list. The only difference is the data in the PRIOR register
of the GTIA chip. The shadow register for PRIOR is GPRIOR [$026F
(623)].
Mode 8 (PRIOR = $00 - $3F (0 - 63)), uses a screen of 320 columns by
192 rows. Each byte controls 8 pixels as in modes 4 and 6.
Mode 9 (PRIOR = $40 - $7F (64 - 127)) uses a screen of 80 columns by
192 rows. Each byte controls 2 pixels. The pixels are all of the
same color, controlled by COLBK. Each half of a byte in the display
buffer controls the luminance of the assigned pixel. The format of
each byte is as follows.
7 6 5 4 3 2 1 0
-----------------
| data | data |
-----------------
pixel 1|pixel 2
Mode 10 (PRIOR = $80 - $BF (128 - 191), is the same as mode 9 except 9
color luminance combinations are available. The data in each half
byte chooses one of the 9 color registers for the assigned pixel.
Mode 11 (PRIOR = $C0 - FF (192 - 255), is the same as mode 9 except
there is one brightness but 16 colors. The pixel data chooses one of
the 16 available colors. The luminance is that of the background
(COLBK).
USING THE SCREEN HANDLER
OPENING A CHANNEL TO THE SCREEN HANDLER
When a channel is opened to the screen handler the following actions
take place:
The area of memory to be used for the screen data is cleared.
A display list (program for the ANTIC chip) is set up for the proper
graphics mode.
The top-of-free-memory pointer, MEMTOP [$02E5,2 (741)], is set to
point to the last free byte before the display list.
Before opening a channel to the screen handler, the pointer to the
highest memory address needed by the program, APPMHI [$000E,2 (14)],
should be properly set. This will prevent the screen handler from
erasing part of the program when it sets-up the screen data region.
When the channel is opened, two special options can be sent with the
direction parameter (ICAX1).
ICAX1 for screen open
7 6 5 4 3 2 1 0
-----------------
| C S W R |
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
C 1 = don't clear the screen
S 1 = split screen
R 1 = input
W 1 = output
Before the open command, the graphics mode number is placed into
ICAX2.
ICAX2 for screen open
7 6 5 4 3 2 1 0
-----------------
| : mode |
-----------------
mode = $00 through $0B (0 - 11 (0 - 15 on XL/XE))
To open a channel to the screen in BASIC use the GRAPHICS command.
BASIC screen open format
GRAPHICS mode
For Example:
GRAPHICS 8
This will set up a mode 8 graphics screen and open channel 6 to it.
If the graphics mode is 1 - 8, a split screen will be set up. For
example, GRAPHICS 8 will set up a mode 8 screen with a four line text
window at the bottom.
If 16 is added to the mode number, a full screen will be set-up. For
example, GRAPHICS 8+16 or GRAPHICS 24 will set up a mode 8 screen,
with no text window, a full 192 pixels high. If the number 32 is
added to the mode number, the screen will not clear when the channel
opens.
If you want to use a channel other than #6, you will have to use the
open command. It is used in the following format.
screen open without GRAPHICS command
OPEN #channel,direction/special,mode,S:
For example:
OPEN #1,8,7,S:
This will open channel 1 to a mode 7 screen for output only. For use
of special parameters, see ICAX1 above.
USING AN OPEN CHANNEL TO THE SCREEN
Once a channel is opened to the screen it is used like any other input
or output device. In other words, data is placed on the screen by the
PRINT and PUT commands. Data is retrieved from the screen with the
INPUT and GET commands. The part of the screen which the data will be
put in or taken from is determined by the X,Y coordinants in the
database variables COLCRS [$0055,2 (85)] and ROWCRS [$0054 (84)].
What appears on the screen depends on what graphics mode the computer
is in.
Before sending data to the screen in BASIC, a color register must be
assigned to the data. Once a point is plotted on the screen, it's
color will be determined by the color register it was assigned to.
To assign a color to a ploted point, the COLOR command us used as
follows.
COLOR command format
COLOR register
For example,
COLOR 1
After using the above command, all points plotted will be controlled
by color register 1. To change color registers, use the COLOR command
again.
In assembly language, the color is determined by the data sent to the
screen. See the above section on graphics modes for color
information.
In BASIC the PLOT command is used to put data on the screen. The PLOT
command is used as follows.
The BASIC PLOT command
PLOT x,y
x and y are the horizontal and vertical coordinates for the plotted
point.
In modes 3 through 11 a single point will be plotted. In modes 1 and
2 a text character will be printed on the screen by the PLOT command.
The PRINT and PUT commands can also be used in basic. What appears on
the screen depends on the graphics mode.
In modes 1 and 2 the ATASCII characters sent to the screen will be
printed just as in mode 0. See the paragraph on modes 1 and 2 above
for more information. In the other modes what appears depends on how
the ANTIC chip interprets the data bytes sent to the screen. For
example, in mode 8, even numbered characters will be single pixels in
color 1. Odd numbered characters will be in color 0 (background).
There are two special commands for the screen handler, DRAW and FILL
DRAW (ICCOM = $11 (17))
The draw command works exactly like the plot command except a straight
line is drawn from the previous pixel to the new one. In BASIC it is
used in the following format.
the BASIC DRAW command
DRAWTO x,y
FILL (ICCOM = $12 (18))
Fill works like draw except the area to the right of the drawn line
will be filled with the color in FILDAT [$02FD (765)]. The fill
command expects to find a boundary to the right. If no boundary is
found, the entire horizontal screen between the ends of the line is
filled.
To use the fill command in BASIC the XIO command must be used in the
following format.
POSITION x,y
XIO 18 #6,0,0,"E:"
Note that the cursor is first moved by the POSITION command. Below is
an example of how to prepare for and use the fill command.
using the fill command
2nd DRAWTO .____. DRAWTO here
| |
| |
| |
fill to here ! ! PLOT here
This will draw and fill a box on the screen.
THE COLOR REGISTERS
There are nine bytes of memory which control the colors on the screen.
These bytes are called color registers. The color registers have the
following names and relationships.
Color registers and relationships
Register Register modes
name address
0 & 8 1 & 2 3 5 7 4 & 6 9 & 11
10
HEX decimal COLOR numbers
PCOLR0 $02C0 704
0
PCOLR1 $02C1 705
1
PCOLR2 $02C2 706
2
PCOLR3 $02C3 707
3
COLOR0 $02C4 708 0 - 63 1 1
4
COLOR1 $02C5 709 1 - 255 64 -127 2
5
COLOR2 $02C6 710 0 128-191 3
6
COLOR3 $02C7 711 192-255
7
COLOR4 $02C8 712 border backgnd 0 backgnd backgnd
8
The color numbers are in decimal. These are actually shadow
registers. See the O.S. equates below for relationships. In modes 0
- 3 the COLOR number actually determines the character printed
The register to which a pixel/character is assigned to is determined
by the data byte sent to the screen through CIO.
The data in the color registers in in the following format.
Color register data format
7 6 5 4 3 2 1 0
-----------------
| color |bright |
-----------------
color = one of 16 possible colors
bright = one of 8 possible brightnesses
(even numbers, 0 - E)
In basic, the COLOR command is used to assign color registers. The
corresponding registers depends on the graphics mode. For example,
COLOR 0 is COLOR2 in mode 8. In most other modes COLOR 0 is COLOR4.
See the above chart for the register relationships.
To change the contents of the color registers in BASIC, the SETCOLOR
command is used. In all modes except mode 10, the SETCOLOR command
refers to the registers COLOR0 to COLOR4.
SETCOLOR/register relationships
SETCOLOR 0 COLPF0 (COLOR0)
SETCOLOR 1 COLPF1 (COLOR1)
SETCOLOR 2 COLPF2 (COLOR2)
SETCOLOR 3 COLPF3 (COLOR3)
SETCOLOR 4 COLBK (COLOR4)
The format for the SETCOLOR command is...
SETCOLOR command format
SETCOLOR register,hue,brightness
register = 0 - 4 (0 - 8 in mode 10)
hue = 0 - 15 (16 colors)
brightness = 0 - 16 (even numbers only (8 brightnesses)
The following chart gives the colors represented by the hue number.
colors represented by hue numbers
0 grey 8 blue
1 gold 9 cyan
2 gold-orange 10 blue-green
3 red-orange 11 blue-green
4 orange 12 green
5 magenta 13 yellow-green
6 purple-blue 14 yellow
7 blue 15 yellow-red
The attract mode
If a key is not pressed for more than 9 minutes the computer will
enter the attract mode. This mode is used to prevent burning of the
TV phosphors by lowering the brightness and constantly changing the
colors. The attract mode timer, ATRACT [$004D (77)], is set to 254
($FE) when the the attract mode is entered. To force the computer out
of the attract mode, poke a number less than 127 into ATRACT.
Useful database variables and OS equates
APPMHI $000E,2 (14): lower limit for screen region
ATRACT $004D (77): attract mode timer and flag
LMARGN $0052 (82): left margin
RMARGN $0053 (83): right margin
ROWCRS $0054 (84): horizontal cursor position
COLCRS $0055,2 (85): vertical cursor position
DINDEX $0057 (87): current graphics mode
SAVMSC $0058,2 (88): starting address of display buffer
OLDROW $005A (90): previous cursor position
OLDCOL $005B,2 (91): " " "
OLDCHR $005D (93): character currently at the text cursor
OLDADR $005E,2 (94): memory address of cursor
RAMTOP $006A (106): end-of-RAM + 1 (MSB only)
SDLSTL $0230,2 (560): shadow register of display list address
TXTROW $0290 (656): text window cursor position
TXTCOL $0291,2 (657): " " " "
TXTMSC $0294,2 (660): starting address of text window data buffer
RAMSIZ $02E4 (740): permanent end-of-RAM + 1 (MSB only)
CRSINH $02F0 (752): cursor inhibit, 1 = no cursor
FILDAT $02FD (765): color data for fill
DSPFLG $02FE (766): if >0 screen control codes are displayed as
ATASCII characters (EOL is uneffected)
SSFLAG $02FF (767): > 0 = stop screen print
COLPM0 $D012 (53266): actual color registers
COLPM1 $D013 (53267): loaded from shadow
COLPM2 $D014 (53268): registers during
COLPM3 $D015 (53269): vertical blank
COLPF0 $D016 (53270):
COLPF1 $D017 (53271): see above
COLPF2 $D018 (53272): for use
COLPF3 $D019 (53273):
COLBK $D020 (53274):
OS shadow registers
PCOLR0 $02C0 (704): COLPM0
PCOLR1 $02C1 (705): COLPM1
PCOLR2 $02C2 (706): COLPM2
PCOLR3 $02C3 (707): COLPM3
COLOR0 $02C4 (708): COLPF0
COLOR1 $02C5 (709): COLPF1
COLOR2 $02C6 (710): COLPF2
COLOR3 $02C7 (711): COLPF3
COLOR4 $02C8 (712): COLBK
CHAPTER 9
THE RESIDENT DISK HANDLER
The resident disk handler is separate from DOS and is part of the
permanent operating system ROM. The disk handler does not use CIO.
The resident disk handler works with one sector at a time. It is used
by setting the drive number, sector number, and operation code in the
device control block. The program then jumps (JSR) to the handler
entry vector, DSKINV [$E453 (58451)].
Device control block (for resident disk handler)
DDEVIC [$0300 (768)]
Serial bus I.D. Set by handler
DUNIT [$0301 (769)]
Drive number
DCOMND [$0302 (770)]
Command byte
DSTATS [$0303 (771)]
status byte
DBUFLO [$0304 (772)]
DBUFHI [$0305 (773)]
Pointer to 128 byte memory block for data storage.
DTIMLO [$0306 (774)]
Timeout value (response time limit) in seconds
DBYTLO [$0308 (776)]
DBYTHI [$0309 (777)]
number of bytes transferred, set by handler
DAUX1 [$030A (778)]
DAUX2 [$030B (779)]
sector number
DISK HANDLER COMMANDS
GET SECTOR
Before the JSR to DSKINV is made the following parameters are set.
GET SECTOR parameters
DCOMND = $52 (82)
DUNIT = (1 - 4)
DBUFHI
and
DBUFLO = address of 128 byte buffer
DAUX1
and
DAUX2 = Sector number (LSB,MSB)
This operation will read the specified sector and put the data into
the specified buffer.
PUT SECTOR
PUT SECTOR is used the same as GET SECTOR except for DCOMND.
PUT SECTOR parameters
DCOMND = $50 (80)
This operation sends the data in the specified buffer to the specified
disk sector.
PUT SECTOR WITH VERIFY
PUT SECTOR WITH VERIFY is used the same as PUT SECTOR except for
DCOMND.
PUT SECTOR WITH VERIFY parameters
DCOMND = $57 (87)
This operation sends the data in the specified buffer to the specified
disk sector then checks for errors.
GET STATUS
Only the DUNIT and DCOMND need to be set
GET STATUS parameters
DCOMND = $53 (83)
DUNIT = (1 - 4)
The status information will be put in three bytes starting at DVSTAT
[$02EA (746)].
Status format
7 6 5 4 3 2 1 0
-----------------
DVSTAT + 0 | command stat |
-----------------
+ 1 | hardware stat |
-----------------
+ 2 | timeout value |
-----------------
The command status byte gives the following information.
Bit
0 1 = invalid command frame received
1 1 = invalid data frame received
2 1 = unsuccessful PUT operation
3 1 = disk is write protected
4 1 = active/standby
The hardware status byte contains the status register of the ISN1771-1
disk controller chip.
The timeout byte contains the maximum allowable response time for the
drive in seconds.
FORMAT DISK
The handler will format then verify the the disk. The numbers of all
bad sectors (up to 63) will be put into the specified buffer followed
by two bytes of $FF.
The following parameters are set before the call.
FORMAT parameters
DCOMND = $21 (33)
DUNIT = (1 - 4)
DBUFLO
and
DBUFHI = address of bad sector list (buffer)
After the operation the status byte is set. Also, DBYTLO and DBYTHI
will contain the number of bytes of bad sector information (not
including the two $FF bytes).
Useful data base variables and OS equates
DVSTAT $02EA,3 (746): device status block, 3 bytes
DDEVIC $0300 (768): serial bus I.D.
DUNIT $0301 (769): device number
DCOMND $0302 (770): command byte
DSTATS $0303 (771): status byte
DBUFLO $0304 (772): data buffer
DBUFHI $0305 (773): pointer
DTIMLO $0306 (774): timeout value
DBYTLO $0308 (776): number of bytes transfered
DBYTHI $0309 (777):
DAUX1 $030A (778): sector
DAUX2 $030B (779): number
DSKINV $E453 (58451): disk handler entry vector
CHAPTER 10
SYSTEM INTERRUPTS
There are four types of interrupts which can occur with the 6502
microprocessor:
6502 interrupts
1. chip reset
2. IRQ, interrupt request (maskable)
3. MNI (non-maskable interrupt)
4. software interrupt (BRK instruction)
CHIP RESET
On the 400/800 the chip reset occurs only upon power-up and causes the
computer to do a cold start. On later models, pressing [SYSTEM RESET]
will cause a chip reset but the computer then does a warm start. On
the 400/800, the [SYSTEM RESET] key generates a NMI interrupt.
COLD START
This is a synopsis of the cold start routine.
1
The warm start flag [$0008] is set to 0 (false)
2
If a cartridge slot contains a diagnostic cartridge, control is handed
to the cartridge.
3
The end of RAM is determined by trying to complement the first byte of
each 4K block of memory.
4
Hardware registers at $D000 - $D4FF (except $D100 - $D1FF) are
cleared.
5
RAM is cleared from $0008 to the top of ram.
6
The user program jump vector, DOSVEC [$000A] is set to point to the
black board mode (Atari logo display mode in XL/XE models).
7
The screen margins are set to 2 and 39
8
Interrupt vectors are initialized.
9
Bottom of free RAM pointer, MEMLO [$02E7], is set to point to $0700.
10
Resident CIO handlers are initialized.
11
If the [START] key is pressed the cassette boot request flag, CKEY
[$004A], is set.
12
The CIO device table is initialized.
13
If a cartridge is present it is initialized.
14
Channel 0 is opened to the screen editor. The top-of-free-RAM
pointer, MEMTOP [$02E5], is set to point below the screen region. The
computer then waits for the screen to be established before
continuing.
15
If the cassette boot flag is set the cassette is booted.
16
If there is no cartridge present or a cartridge doesn't prevent it,
the disk is booted.
17
The cold start flag is reset.
18
If there is a cartridge present, the computer jumps to the cartridge's
run vector.
19
If there is no cartridge present the computer jumps through the vector
DOSVEC [$000A (10)]. DOSVEC will point to either a booted program,
the memo pad routine (400/800) or the logo display routine (XL/XE).
WARM START
1
The warm start flag is set to $7F (true).
2
cold start steps 2 - 4 are executed.
3
RAM is cleared from $0010 - $007F and $0200 - $03FF.
4
Cold start steps 7 - 14 are executed.
5
If cassette booted software is present the computer JSRs through
CASINI [$0002].
6
If disk booted software is present the computer JSRs through DOSINI
[$000C (12)].
The difference between cold start and warm start is the condition of
the warm start flag, WARMST, [$0008]. If this flag is 0 a complete
cold start is executed. If the flag is anything other than 0 then
only the warm start part of the warm start/cold start code is
executed.
NON-MASKABLE INTERRUPTS (NMI)
NMI interrupts are generated by the following conditions:
1. Display list interrupt, generated by the ANTIC chip.
2. TV vertical blank interrupt, generated by the ANTIC
chip.
3. [SYSTEM RESET] key (400/800).
When an NMI interrupt occurs, the hardware register NMIST [$D40F] is
examined to determine what type of interrupt occurred. The computer
is then directed through the proper ram vector to service the
interrupt.
DISPLAY LIST INTERRUPTS (DLIs)
The computer makes no use of DLIs. The ram vector points to an RTI
instruction.
VERTICAL BLANK INTERRUPTS (VBIs)
There are two stages to the VBI service routine. The second stage is
only done if a critical function was not interrupted.
Stage 1 (VBI)
The real time clock, RTCLOK [$0012 - $0014], is incremented.
The attract mode variables are processed.
System timer 1 is decremented. If it goes to zero the computer JSRs
through system time-out vector 1.
Stage 2 (VBI)
The hardware registers are loaded with the data in their shadow
registers.
System timer 2 is decremented. If it goes to zero the computer JSRs
through the system time-out vector 2.
System timers 3, 4, and 5 are decremented. If a timer goes to zero
the computer sets system timer flags 3, 4, and/or 5.
If auto-repeat is active, the auto-repeat process is done.
The keyboard debounce timer is decremented if not 0.
Information at the controller port registers is read, processed and
placed in the proper shadow registers.
[SYSTEM RESET] INTERRUPT
If a [SYSTEM RESET] interrupt is generated on the 400/800 the computer
jumps to the warm start routine.
INTERRUPT REQUESTS (maskable interrupts (IRQs))
When an IRQ interrupt occurs the hardware register IRQST [$D20E], the
PIA status registers, PACTL [$D302] and PBCTL [$D303] are examined to
determine what caused the interrupt.
For each interrupt, the 6502 accumulator is pushed to the stack. The
computer is then directed to the proper ram vector to service the
interrupt.
SOFTWARE INTERRUPT (BRK instruction)
The operating system doesn't use software interrupts. The software
interrupt vector points to a PLA followed by an RTI.
Interrupt vectors
Label address type function
VDSLST $0200 NMI DLI Points to an RTI
VVBLKI $0222 NMI stage 1 VBI
VVBLKD $0224 NMI return-from-interrupt routine
CDTMA1 $0226 NMI time-out 1 (used by SIO)
CDTMA2 $0228 NMI time-out 2 (not used by OS)
VPRCED $0202 IRQ not used (points to PLA,RTI)
VINTER $0204 IRQ not used (PLA,RTI)
VKEYBD $0208 IRQ keyboard interrupt
VSERIN $020A IRQ used by Serial I/O routine
VSEROR $020C IRQ used by SIO
VSEROC $020E IRQ used by SIO
VTIMR1 $0210 IRQ not used by OS (PLA,RTI)
VTIMR2 $0212 IRQ not used by OS (PLA,RTI)
VTIMR4 $0214 IRQ ?
VIMIRQ $0216 IRQ main IRQ code
VBREAK $0206 BRK unused by OS (PLA,RTI)
SYSTEM TIMERS
The following timers are updated during vertical blank (VBI) as noted
above. If a timer is decremented to 0 the computer jumps through it's
associated vector or sets it's associated flag.
Label address flag/vector
RTCLOK $0012 3 byte clock ($0012 = MSB)
CDTMV1 $0218 CDTMA1 $0226 vector (SIO time-out)
CDTMV2 $021A CDTMA2 $0228 vector
CDTMV3 $021C CDTMF3 $022A flag
CDTMV4 $021E CDTMF4 $022C flag
CDTMV5 $0220 CDTMF5 $022E flag
HARDWARE INTERRUPT CONTROL
There are two registers on the antic chip which control interrupts.
These registers can be used to disable interrupts if necessary. There
are also two associated interrupt status registers.
The IRQ enable and status registers use the same address. The result
is that reading the register does not reveal the enabled interrupts
but the interrupts pending. IRQ interrupt enable data should usually
be written to the OS shadow first. Reading the OS shadow tells which
interrupts are enabled.
Non maskable interrupt enable
NMIEN $D40E
7 6 5 4 3 2 1 0
-----------------
| | | not used |
-----------------
bit 7 1 = DLI enabled
6 1 = VBI enabled
Non maskable interrupt status
NMIST $D40F
7 6 5 4 3 2 1 0
-----------------
| | | | not used|
-----------------
bit 7 1 = DLI pending
6 1 = VBI pending
5 1 = [SYSTEM RESET] key pending
Interrupt request enable
IRQEN $D20E
7 6 5 4 3 2 1 0
-----------------
| | | | | | | | |
-----------------
bit 7 1 = [BREAK] key interrupt enable
6 1 = keyboard interrupt enable
5 1 = serial input interrupt enable
4 1 = serial output interrupt enable
3 1 = serial output-finished interrupt enable
2 1 = timer 4 interrupt enable
1 1 = timer 2 interrupt enable
0 1 = timer 1 interrupt enable
IRQEN has a shadow register, POKMSK [$0010 (A)].
Interrupt request status
IRQST $D20E
7 6 5 4 3 2 1 0
-----------------
| | | | | | | | |
-----------------
bit 7 1 = [BREAK] key interrupt pending
6 1 = keyboard interrupt pending
5 1 = serial input interrupt pending
4 1 = serial output interrupt pending
3 1 = serial output-finished interrupt pending
2 1 = timer 4 interrupt pending
1 1 = timer 2 interrupt pending
0 1 = timer 1 interrupt pending
WAIT FOR HORIZONTAL SYNC
Writing any number to WSYNC [$D40A (54282)] will cause the computer to
stop and wait for the next TV horizontal sync.
It is wise to use DLIs one TV line before needed then writing to
WSYNC. This will keep other interrupts from causing DLIs to be
serviced late. This can cause a DLI to change something in the middle
of a scan line.
Useful database variables and OS equates
POKMSK $0010 (16): IRQEN shadow
IRQEN $D20E (53774): enables IRQs when written to
IRQST $D20E (53774); gives IRQs waiting when read
PACTL $D302 (54018): bit 7 (read) peripheral A interrupt status
bit 0 (write) peripheral A interrupt enable
PBCTL $D303 (54019): bit 7 (read) peripheral B interrupt status
bit 0 (write) peripheral B interrupt enable
WSYNC $D40A (54282): wait for horizontal sync
NMIEN $D40E (54286): NMI enable
NMIST $D40F (54287): NMI status
CHAPTER 11
THE FLOATING POINT ARITHMETIC PACKAGE
The routines which do floating point arithmetic are a part of the
operating system ROM. The Atari computer uses the 6502's decimal math
mode. This mode uses numbers represented in packed Binary Coded
Decimal (BCD). This means that each byte of a floating point number
holds two decimal digits. The actual method of representing a full
number is complicated and probably not very important to a programmer.
However, for those with the knowledge to use it, the format is given
below.
Floating point number representation
byte 0 xx excess 64 exponent + sign
xx \
xx \
xx > 10 BCD digits
xx /
byte 7 xx /
The decimal point is shifted to left of the MSD and the exponent is
adjusted accordingly. Therefore, the decimal point doesn't need to be
represented.
For programming purposes, floating point numbers can be in ASCII code.
It takes up to 14 bytes to store a floating point number in this
manner. The floating point package has a routine to convert numbers
between ASCII and floating point.
USE OF THE FLOATING POINT PACKAGE
The floating point package has several routines to convert between
ASCII and FP and to do the arithmetic functions. These are the
important data base variables.
Floating point data base variables
FR0 $00D4,6 (212): 6 byte buffer for floating point number
FR1 $00E0,6 (224): 6 byte buffer for floating point number
CIX $00F2 (242): index for INBUFF address
INBUFF $00F3,2 (243): 2 byte pointer to ASCII floating point number
FLPTR $00FC,2 (252): 2 byte pointer to user buffer for floating
point number
LBUFF $0580,? (1408): result buffer for FASC routine
MAKING THE CALL
To do a floating point function, first set the proper pointers and JSR
to the operation entry point. Below is a list of the entry points and
parameters.
ASCII to floating point
Converts ASCII representation pointed to by INBUFF to FP in FR0.
AFP = $D800
INBUFF = address of ASCII number
CIX = buffer offset if any
JSR AFP
FLOATING POINT TO ASCII
Converts floating Point number in FR0 to ASCII. The result will be
in LBUFF. INBUFF will point to the ASCII number which will have the
bit 7 of the last byte set to 1.
FASC = $D8E6
JSR FASC
INTEGER TO FLOATING POINT CONVERSION.
Converts a 2 byte unsigned integer (0 to 65535) in FR0 to floating
point in FR0.
IFP = $D9AA
JSR IFP
FLOATING POINT TO INTEGER CONVERSION.
Converts floating point number in FR0 to 2 byte integer in FR0.
FPI = $D9D2
JSR FPI
BCS overflow
ADDITION
Adds floating point numbers in FR0 and FR1 with result in FR0.
FADD = $DA66
JSR FADD
BCS out of range
SUBTRACTION
subtracts FR1 from FR0 with the result in FR0.
FSUB = $DA60
JSR FSUB
BCS out of range
MULTIPLICATION
Multiplies FR0 by FR1 with the result in FR0.
FMUL = $DADB
JSR FMUL
BCS out of range
DIVISION
Divides FR0 by FR1 with result in FR0.
FDIV = $DB28
JSR FDIV
BCS out of range or divisor is 0
LOGARITHMS
Puts logarithm of FR0 in FR0
LOG = $DECD
LOG10 = $DED1
JSR LOG ;for natural log.
or
JSR LOG10 ;for base 10 log.
BCS negative number or overflow
EXPONENTIATION
Put exponentiation of FR0 in FR0
EXP = $DDC0
EXP10 = $DDCC
JSR EXP ;for e ** Z
or
JSR EXP10 ;for 10 ** Z
POLYNOMIAL EVALUATION
Puts the result of an n degree polynomial evaluation of FR0 in FR0.
PLYEVL = $DD40
LDX LSB of pointer to list of floating point
coefficients, ordered high to low.
LDY MSB of above
LDA number of coefficients in list
JSR PLYEVL
BCS overflow
CLEAR FR0
Sets FR0 to all zeroes
ZFR0 = $DA44
JSR ZFR0
CLEAR ZERO PAGE FLOATING POINT NUMBER
Clears user floating point number in page zero.
ZF1 = $DA46
LDX address of zero page FP buffer
JSR ZF1
LOAD FR0 WITH FLOATING POINT NUMBER
Loads FR0 with user FP number in buffer pointed to by 6502 X and Y
registers or by FLPTR. After either operation below, FLPTR will point
to the user FP buffer.
FLD0R = $DD89
LDX lsb of pointer
LDY msb
JSR FLD0R
or
FLD0P = $DD8D
FLPTR = address of FP number
JSR FLD0P
LOAD FR1 WITH FLOATING POINT NUMBER
Loads FR1 with user FP number in buffer pointed to by 6502 X and Y
registers or by FLPTR. After either operation below, FLPTR will point
to the user FP buffer.
FLD1R = $DD98
LDX lsb of pointer
LDY msb
JSR FLD1R
or
FLD1P = $DD9C
FLPTR = address of FP number
JSR FLD1P
STORE FR0 IN USER BUFFER
stores the contents of FR0 in user FP buffer pointed to by 6502 X and
Y registers or by FLPTR. After either operation below, FLPTR will
point to the user FP buffer.
FST0R = $DDA7
LDX lsb of pointer
LDY msb
JSR FST0R
or
FST0P = $DDAB
FLPTR = address of FP number
JSR FST0P
MOVE FR0 TO FR1
Moves the contents of FR0 to FR1
FMOVE = $DDB6
JSR FMOVE
The usual use sequence of the floating point package might be to:
load FR0 and FR1 with FP numbes from user specified buffers
do the math
then store FR0 in a user buffer.
An alternative might be to:
convert an ASCII representation to FP (the result is automatically in
FR0).
move FR0 to FR1.
Convert the second ASCII number.
Do the math.
Convert FR0 back to ASCII.
Store the number back into a user buffer.
The floating point package uses the following blocks of RAM.
RAM used by floating point package
$00D4 - $00FF
$057E - $05FF
If the floating point package is not used the above ram is free.
Useful data base variables and OS equates
FR0 $00D4,6 (212): system FP buffer
FR1 $00E0,6 (224): system FP buffer
CIX $00F2 (242): INBUFF index
INBUFF $00F3,2 (243): pointer to ASCII FP buffer
FLPTR $00FC,2 (252): pointer to user FP buffer
LBUFF $0580 (1408): result buffer for FP to ASCII
AFP $D800 (55296): ASCII to FP
FASC $D8E6 (55526): FP to ASCII
IFP $D9AA (55722): integer to FP
FPI $D9D2 (55762): FP to integer
ZFR0 $DA44 (55876): clear FR0
ZF1 $DA46 (55878): clear zero page FP buffer
FSUB $DA60 (55904): FR0 - FR1
FADD $DA66 (55910): FR0 + FR1
FMUL $DADB (56027): FR0 * FR1
FDIV $DB28 (56104): FR0 / FR1
FLD0R $DD89 (56713): load FR0 by X,Y pointer
FLD0P $DD8D (56717): load FR0 by FLPTR pointer
FLD1R $DD98 (56728): load FR1 by X,Y pointer
FLD1P $DD9C (56732): load FR1 by FLPTR pointer
FST0R $DDA7 (56743): store FR0 at buffer by X,Y pointer
FST1P $DDAB (56747): store FR0 at buffer by FLPTR pointer
FMOVE $DDB6 (56758): move FR0 to FR1
EXP $DDC0 (56768): e exponentiation
EXP10 $DDCC (56780): base 10 exponentiation
PLYEVL $DD40 (56640): polynomial evaluation
LOG $DECD (57037): natural log of FR0
LOG10 $DED1 (57041): base 10 log of FR0
CHAPTER 12
Boot software formats
There are three ways which programs may be booted (loaded
automatically upon power-up):
From the disk drive
From the cassette recorder
From a ROM cartridge
DISK BOOTED SOFTWARE
The disk drive is the primary source for programs (other than the
BASIC interpreter in the computer ROM). A program booted from disk
must be a machine language program. Secondly, the program is arranged
on disk in a different manner from the DOS files.
When the computer is first turned on, it will attempt to read a
program starting at sector one in disk drive one. The exceptions are,
if a cartridge prevents the disk boot process or the [START] key is
pressed. The program is expected to use all 128 bytes of each
sector.
FORMAT OF A DISK BOOTED PROGRAM
A disk booted program begins at sector one on the disk and continues
in sequence. The first six bytes of the first sector contain program
information. The rest of the bytes contain the program itself.
Disk boot program header
1st byte $00 flags, stored in DFLAGS [$0240]
$xx number of sectors used by program
$xx address to start load
$xx
$xx initialization address
6th byte $xx
7th byte $xx start of program
The flags byte is usually unused and should be zero.
The load address is stored in BOOTAD [$0242,2 (578)].
The initialization address is stored in DOSINI [$000C,2 (12)].
After the program is completely loaded the computer will JSR to the
address stored in DOSINI for initialization. It will then jump to the
address stored in DOSVEC to run the program.
The initialization part of the program should set the
bottom-of-free-RAM pointer, MEMLO [$02E7,2 (743)], to point to the end
of the program + 1. This will protect the program from the computer
and other programs. The top-of-user-RAM pointer, APPMHI [$000E,2
(14)], is also usually set to point to the same address. This will
protect the program from the video hardware. It must also set DOSVEC
[$000A,2 (10)] to actually point to the run address of the program.
The initialization should of course end with and RTS. With DOSINI and
DOSVEC properly set, the program will restart up pressing the [SYSTEM
RESET] key.
Rmember that the load address of the program should be six bytes
before where you want the program to reside in memory. The six byte
header will load at the specified start address followed by the
program.
CASSETTE BOOTED SOFTWARE
The cassette boot process is nearly identical to the disk boot
process. The processes are so similar that cassette boot programs can
usually be transferred directly to disk and vice-versa. The two
differences are:
The cassette is booted instead of the disk if the [START] key is
pressed when the power is turned on.
A bug in early operating systems requires the booted program to turn
off the cassette motor with the following command.
LDA #$3C
STA PACTL [$D302]
CARTRIDGE BOOTED SOFTWARE
The Atari 800 has two cartridge slots. All other models have only
one. The second cartridge slot, slot B on the 800, resides from $8000
to $9FFF. The first slot, slot A, resides from $A000 to BFFF. If a
cartridge is inserted in a slot it will disable any RAM in the same
area.
Slot A, which is present in all models, can reside at the entire 16K
used by both cartridges in the 800 ($8000 to $BFFF).
Cartridges use the last six bytes for boot information. In cartridge
A these bytes are from $BFFA to $BFFF. In cartridge B they are from
$9FFA to 9FFF.
last six bytes of a cartridge
$9FFA or $BFFA xx start address
xx
00
xx flag byte
xx init address
$9FFF or $BFFF xx
Flag byte
bit 0 1 = allow disk boot
bit 2 0 = do not start cartridge after init
bit 7 1 = cartridge takes control before OS is
initialized
The initialization process for the cartridge should be similar to that
for disk and cassette. A minimum of an RTS instruction is required.
The third byte of the cartridge tailer is used by the OS to check for
the presence of a cartridge. This byte must be zero.
A 16K cartridge will use both cartridge areas and the cartridge B
tailer area can be used for program code.
THE CARTRIDGE HARDWARE
Most cartridges consist of two ROM chips on a single circuit board.
Moreover, both chip sockets have identical pin assignments. In other
words, the chips can be switched to opposite sockets and the
cartridge will still work. The difference is in the chips themselves.
On one chip, the A12 pin acts as an active-low chip select. On the
other the A12 pin acts as an active-high chip select. Therefore the
state of the A12 pin selects between the two chips.
Cartridge slot pin assignments
BACK
111111
543210987654321
---------------
---------------
SRPNMLKJHFEDCBA
FRONT
1 1 = 16K A A13 (16K only)
2 A3 B GND
3 A2 C A4
4 A1 D A5
5 A0 E A6
6 D4 F A7
7 D5 H A8
8 D8 J A9 __
9 D1 K A12 (CS)/(CS)
10 D0 L D3
11 D6 __ M D7
12 (CS) N A11
13 +Vcc P A10
14 +Vcc R NC
15 NC S NC
The BASIC interpreter resides in the memory used by cartridge A. In
400, 800 and 1200XL models, a BASIC cartridge is required to run BASIC
programs. On other XL and XE models, inserting a cartridge into the
slot or pressing the [OPTION] key upon power-up will disable the
internal BASIC ROM. If BASIC is disabled without inserting another
cartridge, the area from $A000 to $BFFF will contain RAM.
Useful data base variables and OS equates
APPMHI $000E,2 (14): low limit of screen region
DOSVEC $000A,2 (10): run and program reset vector
DOSINI $000C,2 (12): init and reset init
CARTB $8000 (32768): start of cartridge B
CARTA $A000 (40960): start of cartridge A
PACTL $D302 (54018): port A control register Bit 3
controls the cassette motor
CHAPTER 13
THE SERIAL INPUT/OUTPUT INTERFACE (SIO)
Most input and output with the Atari computer passes through the
serial I/O bus. The SIO interface is rather complicated but you are
unlikely to need to use it directly. CIO usually handles SIO for you.
However, if you want to design your own I/O device and it's associated
handler, you need to know how to use the SIO.
SIO transfers data at a rate of 19,200 baud on separate input and
output lines. The data is sent one byte at a time, LSB first, in an
asynchronous format. There are also clock-in and clock-out lines.
There is a signal on the clock-out line but it is not used by any
present devices. The clock-in line is available for synchronous
transfer but is not used by the OS. The signal on the clock-out line
goes high at the leading edge of each bit and goes low in the middle
of each bit.
One byte of SIO data
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
| | | | | | | | | | | | | | | | clock
-------------+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +------
---------+ +---+ +-------+ +--------
| 0 | 1 | 0 | 1 1 | 0 0 | 1 data
+-------+ +---+ +-------+
| |
start bit stop bit
The SIO interface is used much like the resident disk handler. In
fact, it uses the same device control block as the resident disk
handler. After the control block parameters are set, a JSR is made to
the SIO entry vector, SIOV, at $E459 (58457).
Device control block (for SIO)
DDEVIC [$0300 (768)]
Serial bus I.D. Set by handler or program.
DUNIT [$0301 (769)]
Device number if more than one.
DCOMND [$0302 (770)]
Device command byte.
DSTATS [$0303 (771)]
Before the SIO call, this byte tells whether the operation is read,
write or that there is no data transfer associated with the command.
After the call this byte will hold the status (error/no error code) of
the operation.
DSTATS format before command
7 6 5 4 3 2 1 0
-----------------
|W|R| not used |
-----------------
If both W and R are 0, there is no data transfer.
DBUFLO [$0304 (772)]
DBUFHI [$0305 (773)]
Points to the data buffer for either input or output.
DTIMLO [$0306 (774)]
Timeout value (response time limit) in 64/60ths of a second to be set
by handler or program.
DBYTLO [$0308 (776)]
DBYTHI [$0309 (777)]
Number of bytes to be transferred, set by handler or program. This
parameter is not required if the DSTATS specifies no data transfer.
DAUX1 [$030A (778)]
DAUX2 [$030B (779)]
These parameters are sent to the device as part of the command frame.
USING THE SIO INTERFACE
All commands on the serial bus must originate from the computer. The
peripherals will present data on the bus only when commanded to do
so.
Any operation on the serial bus begins with a five byte command frame.
While the command frame is being sent, the command line of the serial
connector is 0.
Command frame format
$xx DDEVIC
$xx DCOMND
$xx DAUX1
$xx DAUX2
$xx checksum
The first four bytes of the command frame come from the device control
block. the checksum is the sum of the other four bytes with the carry
added back after each addition.
If both R and W of the DSTATS are 0, no data is sent to, or expected
from the peripheral, after a command frame is sent. However, the
device is usually expected to send an ACK byte ($41) after the command
frame is sent. If the command frame is invalid, an NAK byte ($4E)
should be sent.
If the operation is output (W = 1) the computer will send a data frame
after it receives the ACK of the command frame. It then expects an
ACK after the data frame is sent.
If the operation is an input (R = 1) the computer expects a data frame
from the peripheral after the ACK. With either input or output, a
"complete" code ($43) should be sent to the computer when the
operation is finished. The "complete" code would follow the ACK of
the data frame with an output operation.
If the operation is not completed for some reason, the peripheral
should send an error code ($45) instead of "complete".
SIO data frame
byte 1 $xx\
> data bytes
byte n $xx/
byte n+1 $xx checksum
SIO commands
READ $52
WRITE $57
STATUS $53
PUT $50
FORMAT $21
DOWNLOAD $20
READADDR $54
READ SPIN $51
MOTOR ON $55
VERIFY
SECTOR $56
Present SIO device I.D.s
DISK $31 - $34 (D1 - D4)
PRINTER $40
RS-232-C $50 - $53 (R1 - R4)
THE SERIAL CONNECTOR
The serial connectors on the computer and all peripherials are
identical. Nearly all peripherials have two serial connectors.
Either connector may be used for any connection. The serial bus is
designed so that peripherials can be daisy-chained together. The
following is a diagram of the serial connector.
The serial connector pin-out
1 1
2 4 6 8 0 2
-----------
/o o o o o o\
/o o o o o o o\
-----------------
1 3 5 7 9 1 1
1 3
1 clock in (to computer)
2 clock out
3 data in
4 GND
5 data out
6 GND
7 command (active low)
8 cassette motor control
9 proceed (active low)
10 +5V/ready
11 audio in
12 +12V (400/800)
13 interrupt (active low)
Proceed goes to pin 40 (CA1) of the PIA. It is not used by present
peripherials.
Interrupt goes to pin 18 (CB1) of the PIA. It is not used by present
peripherials.
Pin 10 doubles as a 50mA +5V peripharal power supply and a computer
ready signal.
Useful database variables and OS equates
SIOV $E459 (58457): serial port handler entry
DDEVIC $0300 (768): device ID
DUNIT $0301 (769): device number
DCOMND $0302 (770): command byte
DSTATS $0303 (771): status byte
DBUFLO $0304 (772): data buffer pointer
DBUFHI $0305 (773):
DTIMLO $0306 (774): timout value
DBYTLO $0308 (776): number of bytes to transfer
DBYTHI $0309 (777):
DAUX1 $030A (778): sent to device
DAUX2 $030B (779): sent to device
CHAPTER 14
THE HARDWARE CHIPS
The previous chapters described the operating system of the computer.
The following chapters will examine the hardware which supports the
6502 and the hardware's associated software.
THE GTIA CHIP
The GTIA (George's Television Interface Adapter) is the main video
circuit in the computer. It controls the following functions.
GTIA functions
Priority of overlapping objects
Color and brightness, including information from the antic chip.
Player/missile control.
console switches and game control triggers.
THE ANTIC CHIP
The main job of the ANTIC chip is interpreting the display buffer for
the GTIA chip. The ANTIC chip is somewhat of a processor in it's own
right. The program which runs it is called the display list and
usually resides just before the display buffer in memory.
The ANTIC chip operates independent of the 6502. It operates by
direct memory access (DMA). The ANTIC chip gives a HALT signal the
6502, causing the 6502 to give up control of the address bus. The
ANTIC chip can then read any data it needs to from memory.
ANTIC chip functions
DMA (Direct Memory Access) control.
NMI (Non-Maskable Interrupt) control.
LIGHT PEN READING
WSYNC (wait for horizontal sync)
THE POKEY CHIP
The most important jobs of the POKEY chip are reading the keyboard and
operating the serial port. It also has the following functions.
POKEY chip functions
Keyboard reading.
Serial port.
Pot (game paddles) reading.
Sound generation.
System timers.
IRQ (maskable interrupt) control.
Random number generator.
THE PIA CHIP
The PIA (Parallel Interface Adapter) is a commonly used I/O chip. It
consists of two 8 bit parallel ports with hand shaking lines. In the
Atari, it has the following functions.
Game controller port control (bi-directional).
Peripheral control and interrupt lines.
Registers in the hardware chips are treated as memory addresses. Many
of the registers are write only. These registers cannot be read from
after they are written to. Other registers control one function when
written to and give the status of an entirely different function when
read from. Still other registers are strobes. Any command which
causes the address of one of these registers to appear on the address
bus will cause their functions to be performed.
The write only registers have shadow registers in RAM. Data to be put
in the registers is usually put into the shadow registers. The data
in the shadow registers is automatically moved to the operating
registers during vertical blank.
For register use and address, see the previous chaptes on the
associated functions.
CHAPTER 15
DISPLAY LISTS
[some of this file was lost...]
chip also has a memory scan counter. This register scans the display
buffer for data to be interpreted and displayed. Once loaded, the
memory scan counter's 4 most significant bits are fixed. The result
is that the memory scan counter cannot cross a 4K memory boundary
(i.e. $AFFF to $B000) without being reloaded.
DISPLAY LIST INSTRUCTIONS
There are three basic instructions in the display list. The type of
instruction is determined by bits 0,1,2 and 3 of an instruction byte.
The other four bits give auxilliary parameters for the instruction.
Bit 7 always enables a display list interrupts (DLIs).
Display list instruction format
7 6 5 4 3 2 1 0
-----------------
|I|n|n|n|0|0|0|0|
-----------------
\ / \ /
--- ------
| |
| 0 = display blank lines
|
0-7 = number of blank lines (1-8)
7 6 5 4 3 2 1 0
-----------------
|I|W| | |0|0|0|1|
-----------------
| \ /
| ------
| |
| 1 = jump (3 byte instruction)
|
0 = jump and display one blank line
1 = jump and wait for vertical blank
7 6 5 4 3 2 1 0
-----------------
|I|R|H|V|M|M|M|M|
-----------------
| | | | \ /
| | | | ------
| | | | |
| | | | 2-F = display one line of graphics in
| | | | ANTIC mode 2-F
| | | 1 = horizontal scroll enabled
| | |
| | 1 = vertical scroll enabled
| |
| 1 = reload memory scan counter with next two bytes
|
1 = display list interrupt, all instructions
In the display instruction, the ANTIC mode is different from the CIO
graphics mode. However, each CIO graphics mode uses a particular
ANTIC mode. Below are descriptions of the ANTIC modes with their
associated graphics (CIO) modes.
ANTIC MODE 2 (Graphics 0)
Uses 8 pixel by 8 pixel characters, 40 characters horizontal, 8 TV
scan lines vertical. Only one color can be displayed at a time.
ANTIC MODE 3
8 X 10 pixel, Graphics 0 type characters. This mode requires a custom
character set. The advantage is that it allows true decenders. The
custom C-set is still 8 X 8 pixels. Lower-case letters with decenders
have the bottom row of pixels put on the top row.
Lower-case "y" for ANTIC mode 3
C-set Display
---------- ----------
| XXXXX | | |
| | | |
| | | |
| XX XX | | XX XX |
| XX XX | | XX XX |
| XX XX | | XX XX |
| XXXXX | | XXXXX |
| XX | | XX |
---------- | XXXXX |
| |
----------
ANTIC MODE 4 (graphics 12 on XL and XE)
This mode has characters the same size as graphics 0. However, the
characters are only 4 X 8 pixels. This gives only half the horizontal
resolution of graphics 0. The advantage is that up to four colors of
"graphics 0" characters can be displayed at once. This mode also
requires a custom C-set. Below is a comparison of the normal C-set to
one which works with the ANTIC 4 mode.
Upper-case "A" for ANTIC modes 2 and 4
mode 2 mode 4
---------- ----------
| | | |
| XX | | yy |
| XXXX | | yy |
| XX XX | |xx zz |
| XX XX | |xx zz |
| XXXXXX | |xxyyzz |
| XX XX | |xx zz |
| | | |
---------- ----------
xx, yy and zz represent two bit binary numbers, controlling one pixel
each. These numbers determine which color register a pixel is
assigned to: (COLOR0, COLOR1, COLOR2 or COLOR3).
ANTIC mode 5
Antic mode five is identical to ANTIC mode 4 except the characters are
displayed twice as tall. This makes only 12 lines on the screen.
ANTIC MODE 6 (Graphics 1)
This mode uses 8 X 8 pixel characters except they are displayed twice
as wide as in ANTIC mode 2. There are 3 colors available at once but
only one case (upper or lower) can be displayed at a time. The data
base variable CHBAS [$02F4 (756)] controls the character, [$E0 (224) =
upper-case, $E2 (226) = lower-case]
The color/character is controlled by either the color statement or the
ATASCII number of the character printed. Control characters are
controlled by COLOR0, upper-case characters by COLOR1 and lower-case
characters by COLOR2. Remember that all characters print as
upper-case alpha characters, but of different colors.
ANTIC MODE 7 (Graphics 2)
This mode is identical to mode 6 except the characters are displayed
twice as tall. This results in only 12 lines possible on the screen.
ANTIC MODE 8 (Graphics 3)
This is the first graphics (non-character) mode. This mode, as other
non-character graphics modes do, uses data in the display buffer as a
bit map to be displayed.
A command to display in mode 8 will cause the ANTIC chip to read the
next 10 bytes in the display buffer. Each pair of bits will control
one pixel as in mode 4. However, the pixels are blocks the same size
as a Graphics 0 (ANTIC 2) characters.
ANTIC MODE 9 (Graphics 4)
This is similar to ANTIC mode 8 except each byte controls 8 pixels
(instead of 4) and only one color can be displayed at a time. The
pixels are also half the size of those in ANTIC mode 8.
ANTIC MODE A (Graphics 5)
This mode uses 20 bytes per line/command. As in ANTIC mode 8, each
pair of bits controls one pixel. The result is that the pixels are
the same size as in ANTIC mode 9 but four colors can be displayed at
once.
ANTIC MODE B (Graphics 6)
As in mode A, there are 8 pixels per byte and only one color. The
pixels are half the size as in mode A.
ANTIC MODE C
Like mode B except the pixels are half as tall (only one T.V. line).
ANTIC MODE D (Graphics 7)
40 Bytes per line, each byte controls 4 pixels. The pixels are 1/4 as
large as in ANTIC mode 8 (Graphics 3).
ANTIC MODE E (Graphics 15 on XL and XE)
Like mode D except the pixels are half as tall (one T.V. line). Antic
mode E is sometimes called Graphics 7.5
ANTIC mode F (Graphics 8, 9, 10 and 11)
This is the highest resolution mode. Pixels are 1/8 the size of ANTIC
mode 8 or mode 2 characters. It uses 40 bytes per line, each byte
controlling 8 pixels, unless the GTIA chip intervenes. Only one color
can be displayed at a time.
DISPLAY LIST EXAMPLES
When CIO opens a channel to the screen, it sets up the proper display
list for the ANTIC chip. The following are the things CIO must handle
when setting up the display list.
Display list duties as used by CIO
display a certain number of blank lines at the top of the screen.
Load the memory scan counter with the address of the display data
buffer.
Display the required number of lines in the required ANTIC mode.
Set up a jump instruction if the display list crosses a 1K memory
boundary.
Set up a reload-memory-scan-counter instruction if the display data
buffer crosses a 4K memory boundary.
CIO assumes that the display data buffer will butt against an 8K
memory boundary. If a program causes the display buffer to cross a 4K
boundary (by changing RAMTOP [$006A (106)] to point to an address
which is not at an 8K boundary) the screen will be scrambled. This is
not usually a problem if the graphics mode doesn't require a large
block of memory.
SAMPLE DISPLAY LIST
Below is an example of a Graphics 0 display list as CIO would set it
up.
Display list for Graphics 0
assuming BASIC starts at $A000
address instruction explanation
Dec. Hex.
$9C20 112 $70 \
112 $70 >---- 24 blank lines (8 each command)
112 $70 /
66 $42 ----- load memory scan counter with
$9C24 64 $40 \__ next two bytes and display one line
156 $9C / \ of ANTIC 2 characters
2 $02 -\ |
2 $02 | \- address of display data buffer
2 $02 |
2 $02 \--- 2nd ANTIC 2 instruction
- ---
2 $02 ----- 24th ANTIC 2 instruction
65 $41 \
32 $20 >---- jump back to start of list
156 $9C /
$9C40 ??? ?? first byte of display data buffer
--- --
$9FFF ??? ?? last byte of buffer
$A000 start of ROM
A display list for a higher resolution graphics mode would require
more instructions and might cross a 1K boundary. It would then
include a jump instruction to cross the boundary.
MULTIPLE DISPLAYS
It is possible to set up multiple displays and use one at a time. The
technique of changing from one display to another is called page
flipping. Below is the simplest way to set up two displays.
setting up two displays
Call a graphics mode through CIO or by using a BASIC GRAPHICS
command.
Store the display list pointers, SDLSTL and SDLSTH, and the CIO screen
pointer, SAVMSC [$0058,2 (88)].
Move the start-of-ROM pointer, RAMTOP [$006A (106)] to below the
current display list. RAMTOP is a one byte pointer so it changes in
increments of one page (256 bytes).
make another graphics call as in the first step.
store the new display list pointer and CIO screen pointer.
This will set up two displays, each with it's own display list. If
the displays are in the same graphics mode, or you will not make any
changes in the displays with CIO commands, (PLOT, PRINT, etc.) you can
flip between the two simply by changing the display list pointer.
If the screens are in the same graphics mode and you want to change
which one to do CIO commands to, Change the CIO screen pointer, SAVMSC
[$0058,2 (88)]. This way, you can display one screen while drawing on
the other.
If you want to do CIO commands to screens of different graphics modes,
you will have the move RAMTOP and do a graphics call to change
screens.
If your manipulation of RAMTOP causes the display data buffer to cross
a 4K boundary, the screen may be scrambled.
DISPLAY LIST INTERRUPTS
DLIs are not used by the operating system. However, other programs
can initiate and use them. Use the following steps to set up display
list interrupts.
Setting up DLIs
Set bit 7 of the display list instruction for the line before you want
the interrupt to occur. (The interrupt routine should set WSYNC and
wait for the next line to execute.)
Set bit 7 of NMIEN [$D40E (54286)] to enable DLIs.
Set the DLI routine vector, VDSLST [$0200,2 (512)] to point to your
machine language DLI routine.
Your DLI routine should set WSYNC [$D40A (54282)]. STA WSYNC will do.
THis will cause the 6502 to wait for the next horizontal sync. This
will keep the DLI routine from changing something in the middle of a
T.V. line.
The DLI routine must end with an RTI instruction.
SCROLLING
Scrolling is controlled by a combination of scroll position registers,
and changing the memory scan counter. Basically, course scrolling is
done by reloading the memory scan counter and fine scrolling is done
by changing the scroll registers.
VERTICAL SCROLLING
Vertical scrolling is very simple. Follow the steps below to set up
vertical scrolling of graphics.
Steps to use vertical scrolling
Set bit 4 of the first byte of the display list instruction for each
line to be scrolled.
Put the number of T.V. lines to offset the graphics vertically in the
vertical scroll register, VSCROL [$D405 (54277)]
The vertical scroll register can offset the graphics upward by 0 - 7
T.V. lines in the 24 line graphics modes (ANTIC modes 2 and 4). In 12
line graphics modes (ANTIC modes 5 and 7) it can vertically offset the
graphics by 0 - 15 T.V. lines. To offset the graphics an 8th (or
16th) line, the scroll register is reset to 0 and the memory scan
counter is reloaded with the address of the next line of graphics in
the display data buffer. If the entire screen is being scrolled, the
load-memory-scan-counter command (near the beginning of the display
list) is changed to point to the address of the second line of
graphics.
HORIZONTAL SCROLLING
Horizontal scrolling works much like vertical scrolling. It is
enabled by setting bit 5 of the instruction for each line to be
scrolled. The horizontal scroll register, HSCROL [$D404 (54276)],
sets the offset. The small difference is that graphics are moved
twice as far per change (two graphics 8 pixels instead of one). Also,
when HSCROL = 0 the graphics are offset beyond the left edge of the
screen by 16 color clocks (32 Graphics 8 pixels). When HSCROL = 15,
the graphics line is shifted one color clock (2 Graphics 8 pixels) to
the left of the screen.
The big difference is that the memory scan counter gets messed up.
This means that you must use a reload-memory-scan-counter command for
each line of graphics. This is a major modification of the display
list. It will require you to move and build the list yourself.
The advantage of this is that you can have a scrolling window in a
large graphics map. The technique is to move the window by reloading
the memory scan counter, then fine scrolling to the invisible bytes
beyond the edges of the screen.
useful data base variables and OS equates
SAVMSC $0058,2 (88): pointer to current screen for CIO commands
RAMTOP $006A (106): start-of-ROM pointer (MSB only)
VDSLST $0200,2 (512): DLI vector
RAMSIZ $02E4 (740): permanent start-of-ROM pointer (MSB only)
DLISTL $D402 (54274): display list pointer low byte
DLISTH $D403 (54275): " high byte
HSCROL $D404 (54276): horizontal scroll register
VSCROL $D405 (54277): vertical scroll register
NMIEN $D40E (54286): NMI enable (DLIs)
Shadow registers
SDLSTL $0230 (560): DLISTL
SDLSTH $0231 (561): DLISTH
CHAPTER 16
PLAYER AND MISSILE (PM) GRAPHICS
Players and missiles (called sprites on some computers) are movable
objects which are independent of the normal graphics.
Player and missile graphics are fairly straight forward. Once the
computer is set-up for PM graphics, five 8-pixel-wide columns can be
displayed on the screen. The horizontal resolution (width of each
pixel) and the vertical resolution (number of scan lines per pixel)
are variable. The horizontal position of each column is determined by
it's horizontal position register. Each column is simply a
representation of a bit map in a certain block of memory. If you want
to draw an object on the screen, you simply put a bit map representing
it in the proper memory block. The vertical position of an object is
determined by the location of it's bit map in memory. For example, if
you want to draw a happy face in the middle of the screen, you put a
happy face bit map in the middle of one of the memory blocks
controlling one of the columns.
One column (player) displayed on the screen
---------- first byte of a block
| |
| |
------------------------------
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | ++++ | visible |
| | + + | |
| |+ + + +| |
| |+ +| area |
| |++ ++| |
| |+ ++++ +|--object |
| | + + | bit map |
| | ++++ | |
| | | |
| | | |
| | | |
------------------------------
| |
| |
---------- last byte of a block
Horizontal positions
$00 $30 $CE $FF
(0) (48) (206) (255)
| | | |
| Left edge right edge |
| |
Far left far right
To move the happy face vertically you would move the entire bit map in
memory. To move the happy face horizontally you change the number in
the horizontal position register for the proper player.
One of the players can be (and often is) split into four columns of
two pixels wide each. These columns are then called missiles. In
this case, each missile has it's own horizontal position register.
SETTING UP PM GRAPHICS
PM graphics are enabled by the direct memory access control register,
DMACTL [$D400 (54272)]. The program using PM graphics will usually
use the shadow register, SDMCTL [$022F (559)].
DMACTL (SDMCTL)
7 6 5 4 3 2 1 0
-----------------
|0|0| control |
-----------------
bits
5 1 = enable display list reading
4 0 = one line player resolution
1 = two line player resolution
3 1 = enable four players
2 1 = enable fifth player or missiles
1 & 0 00 = no background
01 = narrow background (128 color clocks,
1 color clock equals 2 GRAPHICS 8 pixels)
10 = normal background (160 color clocks)
11 = wide background (192 color clocks)
Normally, bits 5 and 1 are set to 1. Bits 4, 3 and 2 are used to
enable players and/or missiles accordingly.
Once DMACTL is set up for the type of PM graphics to enable, the
graphics control register, GRACTL [$D01D (53277)], is used to actually
enable the PM graphics.
GRACTL
7 6 5 4 3 2 1 0
-----------------
|not used | | | |
-----------------
Bits
2 1 = latch paddle triggers
1 1 = enable four players
0 1 = enable fifth player or missiles
If only DMACTL is set up, the ANTIC chip will access memory for PM
graphics but will not display them.
Next, the memory area used for the PM bit maps must be set. This
block must start on a 2K (8 page) boundary if single line resolution
is used and a 1K (4 page) boundary for two line resolution.
The page number where the bit map starts is stored in the PM base
register, PMBASE [$D407 (54279)]. For one line resolution this number
will be a multiple of 8. For two line resolution it will be a
multiple of 4. PMBASE holds the MSB of the address of the PM bit map.
The LSB will always be 0 so it need not be specified.
The PM bit maps
2 line resolution
128 bytes (1/2 page)
per player
----------------- start + 0
| |\
+---------------+ 1-1/2 page
| | (384 bytes)
+===============+ unused
| |/
+---------------+ +$180 (384)
|M3 |M2 |M1 |M0 | fifth player or missiles
+===============+ +$200 (512)
| player 0 map |
+---------------+ +$280 (640)
| player 1 map |
+===============+ +$300 (768)
| player 2 map |
+---------------+ +$380 (896)
| player 3 map |
+===============+ +$400 (1024)
1 line resolution
256 bytes (1 page)
per player
----------------- start + 0
| |\
+ +
| |
+===============+
| | 768 bytes
+ +
| | (3 pages)
+===============|
| | unused
+ +
| |/
+===============+ +$300 (768)
| | | | | fifth player
+M3 |M2 |M1 |M0 | or missiles
| | | | |
+===============+ +$400 (1024)
| |
+ player 0 map +
| |
+===============+ +$500 (1280)
| |
+ player 1 map +
| |
+===============+ +$600 (1536)
| |
+ player 2 map +
| |
+===============+ +$700 (1792)
| |
+ player 3 map +
| |
+===============+ +$800 (2048)
Example of using P/M graphics in BASIC
0 REM ---LABEL REGISTERS ETC
10 LINES=2
20 VERT=120
22 IF LINES=2 THEN VERT=VERT/2
30 PM0=1024
32 IF LINES=2 THEN PM0=PM0/2
40 HORIZ=120
50 PCOLR0=704
60 SDMCTL=559
70 SIZEP0=53256
80 HPOSP0=53248
90 SDMCTL=559
100 PMRAM=PEEK(106)-16
110 PMBASE=54279
120 GRACTL=53277
130 PMSTART=PMRAM*256+PM0
200 REM ---SET REGISTERS
210 POKE SDMCTL,62
212 IF LINES=2 THEN POKE SDMCTL,46
220 POKE SIZEP0,1
230 POKE HPOSP0,HORIZ
240 POKE PCOLR0,88
250 POKE PMBASE,PMRAM
260 POKE GRACTL,3
300 REM ---DRAW PLAYER
310 POKE PMSTART+VERT,60
320 POKE PMSTART+VERT+1,66
330 POKE PMSTART+VERT+2,165
340 POKE PMSTART+VERT+3,129
350 POKE PMSTART+VERT+4,195
360 POKE PMSTART+VERT+5,189
370 POKE PMSTART+VERT+6,66
380 POKE PMSTART+VERT+7,60
The above program will draw a happy face in about the middle of the
screen using player 0. To move the player horizontally, poke a
different number into HPOSP0. To draw the player in a different
vertical position, change VERT. To use a different player or missile,
use the memory maps above to find the starting address of the player
you want to use. For example, to use player 1 change line 40 to
PM1=1280. Then change line 130 to PMSTART=PMRAM*256+PM1. The
variable "LINES" determines the vertical resolution. The number poked
into SIZEP0 determines the width.
P/M PRIORITY
The priorities of players, missiles and non-P/M graphics can be
controlled by the PRIOR register [$D10B (53275)] and its shadow
register, GPRIOR [$26F (623)]. Objects with higher priority will
appear to move in front of lower priority objects. The format of
PRIOR is as follows:
PRIOR bit assignment
7 6 5 4 3 2 1 0
-----------------
| | | | | | | | |
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
Bits
7-6 Control the GTIA graphics modes.
00 = normal
01 = mode 9
10 = mode 10
11 = mode 11
5 1 = multiple color player enable. Permits
overlapping of players 0 and 1 or
2 and 3 with a third color in the
overlapped region.
4 1 = fifth player enable. All missiles
will assume the color controlled by
COLOR3 [$2C7 (711)]. missiles are
positioned together to make the fifth
player.
3-0 Controls the priorities of players, missiles
and other graphics. Objects with higher priority will appear to move
in front of those with lower priority.
The following chart may need some clarification. In the chart:
PM0 = player 0 and missile 0
C0 = COLOR0, plotted graphics controlled
by color register 0 in the SETCOLOR
command.
P5 = all four missiles when combined
into one player.
BAK = the background, known as COLOR4 or color
register 4 in the SETCOLOR command.
Etc.
Bits 0-3 of PRIOR and P/M priorities
Bit 3=1 2=1 1=1 0=1
C0 C0 PM0 PM0 highest
C1 C1 PM1 PM1 priority
PM0 C2 C0 PM2
PM1 C3+P5 C1 PM3
PM2 PM0 C2 C0
PM3 PM1 C3+P5 C1
C2 PM2 PM2 C2
C3+P5 PM3 PM3 C3+P5 lowest
BAK BAK BAK BAK priority
Only one priority bit can be set at a time. If more than one priority
bit is 1, overlapping areas of conflicting priorities will turn
black.
COLLISIONS
Each player or missile has a register showing overlap (collisions)
with other objects. Each player has two registers assigned to it; one
to detect collisions with other players and one to detect collisions
with plotted objects. Likewise each missile has two registers; one to
detect collisions with players and one to detect collisions with
plotted objects. Careful use of these 16 registers can detect any
type of collision.
Each register uses only the lower 4 bits. The bits which equal 1 tell
what the associated object has collided with. For example, to detect
collisions of player 1 to other players examine P1PL [$D00D (53261)].
P1PL, player 1 to player collisions
7 6 5 4 3 2 1 0
-----------------
P1PL |unused | | | | |
-----------------
8 4 2 1
3 = 1 collision with player 3
2 = 1 collision with player 2
1 = 1 invalid
0 = 1 collision with player 0
Etc.
When looking for collisions with plotted objects, the bit number tells
what color register is assigned to the object the collision was with.
For example, to detect collisions between player 1 and plotted objects
(officially called the play field), P1PF [$D005 (53253)] is used.
P1PF, player 1 to ploted object collisions
7 6 5 4 3 2 1 0
-----------------
P1PF |unused | | | | |
-----------------
8 4 2 1
3 = 1 collision with COLOR3
2 = 1 " COLOR2
1 = 1 " COLOR1
0 = 1 " COLOR0
Etc.
Once a collision occurs it remains indicated in its collision
register. To clear out all collision registers, write anything to
HITCLR [$D01E (53278)]. STA HITCLR or POKE 53278,0 will do.
Useful database variables and OS equates
HPOSP0 $D000 (53248): write: horizontal position of player 0
M0PF " " : read: missile 0 to plotted graphics collisions
HPOSP1 $D001 (53249): write: horizontal position of player 1
M1PF " " : read: missile 1 to plotted graphics collisions
HPOSP2 $D002 (53250): write: horizontal position of player 2
M2PF " " : read: missile 2 to plotted graphics collisions
HPOSP3 $D003 (53251): write: horizontal position of player 3
M3PF " " : read: missile 3 to plotted graphics collisions
HPOSM0 $D004 (53252): write: horizontal position of missile 0
P0PF " " : read: Player 0 to plotted graphics collisions
HPOSM1 $D005 (53253): write: horizontal position of missile 1
P1PF " " : read: Player 1 to plotted graphics collisions
HPOSM2 $D006 (53254): write: horizontal position of missile 2
P2PF " " : read: Player 2 to plotted graphics collisions
HPOSM3 $D007 (53255): write: horizontal position of missile 3
P3PF " " : read: Player 3 to plotted graphics collisions
SIZEP0 $D008 (53256): write: size of player 0
M0PL " " : read: missile 0 to player collisions
SIZEP1 $D009 (53257): write: size of player 1
M1PL " " : read: missile 1 to player collisions
SIZEP2 $D00A (53258): write: size of player 2
M2PL " " : read: missile 2 to player collisions
SIZEP3 $D00B (53259): write: size of player 3
M3PL " " : read: missile 3 to player collisions
SIZEM $D00C (53260): write: widths for all missiles
P0PL " " : read: player 0 to other player collisions
GRAFP0 $D00D (53261): write: player 0 graphics (used by OS)
P1PL " " : read: player 1 to other player collisions
GRAPF1 $D00E (53262): write: player 1 graphics
P2PL " " : read: player 2 to other player collisions
GRAFP2 $D00F (53263): write: player 2 graphics
P3PL " " : read: player 3 to other player collisions
GRAPF3 $D010 (53264): write: player 3 graphics
GRAFM $D011 (53265): write: missile graphics (used by OS)
COLPM0 $D012 (53266): color for player/missile 0
COLPM1 $D013 (53267): color for player/missile 1
COLPM2 $D014 (53268): color for player/missile 2
COLPM3 $D015 (53269): color for player/missile 3
COLPF0 $D016 (53270): color register 0
COLPF1 $D017 (53271): color register 1
COLPF2 $D018 (53272): color register 2
COLPF3 $D019 (53273): color register 3
COLBK $D01A (53274): background color (register 4)
PRIOR $D01B (53275): priority select, GTIA modes
GRACTL $D01D (53277): graphics control
HITCLR $D01E (53278): writing anything clears all collision bits
DMACTL $D400 (54272): direct memory access (DMA) control
PMBASE $D407 (54279): start of P/M memory
Shadow registers
SDMCTL $022F (559): DMACTL
GPRIOR $026F (623): PRIOR
PCOLR0 $02C0 (704): COLPM0
PCOLR1 $02C1 (705): COLPM1
PCOLR2 $02C2 (706): COLPM2
PCOLR3 $02C3 (707): COLPM3
COLOR0 $02C4 (708): COLPF0
COLOR1 $02C5 (709): COLPF1
COLOR2 $02C6 (710): COLPF2
COLOR3 $02C7 (711): COLPF3
COLOR4 $02C8 (712): COLBK
CHAPTER 17
SOUND
Generating sound can be very simple. For simple sounds there are four
audio channels, each controlled by two control registers.
GENERATING SOUNDS
To generate a sound in channel 1, put the frequency and volume codes
into the frequency and control registers. The frequency register for
channel 1, AUDF1 [$D200 (53760)] can have any number from 0 to $FF
(255). 0 causes the highest frequency; 255 causes the lowest. The
volume/noise (control) register for channel 1, AUDC1 [$D201 (53761)]
is more complicated.
Audio channel control (volume/noise) register
7 6 5 4 3 2 1 0
-----------------
AUDCx | noise | volume|
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
The noise bits can have various values. The best way to learn to use
them is by experimentation. The technical details of the polynomial
counters which generate the noise has little bearing on what is heard.
The two special values of interest are: $1 (volume+16 in decimal),
which causes a DC voltage proportional to the volume bits and; $A
(volume+160), which causes a pure tone (square wave). The volume bits
select the relative volume, 0=off. Therefore, the number, $A8 (168
[8+160]) in AUDC1, will cause the frequency selected by AUDF1 to be a
pure tone of medium volume.
In BASIC the dirty work is done fore you. The SOUND command will do
all the calculations for you. The Sound command format is shown
below.
The BASIC sound command format
SOUND channel,frequency,noise,volume
The channel numbers is 0 to 3 instead of 1 to 4. The frequency, 0 to
255, is put into the frequency register. The noise is put into the
high bits of the channel control register with volume in the low bits.
Therefore...
SOUND 0,125,10,8
will produce a pure tone of medium frequency and volume in channel 0
(called channel 1 in assembly language).
ADVANCED SOUND
The Audio Control register, AUDCTL [$D208 (53768)], (not to be
confused with the four audio channel control registers), adds more
control for assembly language programmers. Again, to go into
technical details will be less productive than experimentation.
The audio control register. (AUDCTL)
7 6 5 4 3 2 1 0
-----------------
AUDCTL | | | | | | | | |
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
7 0 = 17 bit polynomial noise
1 = 9 bit below polynomial noise
6 0 = clock channel 1 with 64 KHz
1 = clock channel 1 with 1.79 MHz
5 0 = clock channel 3 with 64 KHz
1 = clock channel 3 with 1.79 MHz
4 0 = clock channel 2 with 64 KHz
1 = clock channel 2 with channel 1
3 0 = clock channel 4 with 64 KHz
1 = clock channel 4 with channel 3
2 1 = insert logical high-pass filter in
channel 1, clocked by channel 3
1 1 = insert logical high-pass filter in
channel 2, clocked by channel 4
0 0 = 64 KHz main clock
1 = 16 KHz main clock
All bits of AUDCTL are normally zero. The BASIC sound command causes
it to be reset to zero.
By clocking one channel with another, the range can be increased.
This essentially allows two channels with twice the range as each of
the four normal channels. This is called 16 bit sound.
To calculate exact frequencies, use the following formulas. The exact
clock frequencies are also given if more accuracy is needed. The
clock frequencies are acquired by dividing the signal from the TV
color-burst crystal. This crystal has a frequency of 3.579545 MHz.
Clock frequencies:
1.7897725 MHz (color-burst/2)
63.920446 Khz (color-burst/56)
15.699759 KHz (color-burst/228)
Formulas:
For 1.79 MHz
clock clock
f = ------------ f = ------------
2(AUDFn + 7) 2(AUDFn + 4)
16 bit 8 bit
AUDFn is the number in the audio frequency register.
For 16 KHz and 64 KHz
clock
f = ------------
2(AUDFn + 1)
AUDIO TIMER INTERRUPTS
When the audio timers count down to zero they generate IRQ interrupts
(if enabled). The timers can be reset by writing any number to STIMER
[D209 (53769)].
THE CONSOLE SPEAKER
The console speaker is where key clicks and the cassette signals come
from. On XL and XE models this speaker is heard through the TV
speaker. It is operated by toggling bit 3 of CONSOL [$D01F (53279).
This bit always reads 0 but it is actually set to 1 during vertical
blank.
Useful data base variables and OS equates
CONSOL $D01F (53279): bit 3 controls console speaker
AUDF1 $D200 (53760): Audio frequency 1
AUDC1 $D201 (53761): audio control 1
AUDF2 $D202 (53762): Audio frequency 2
AUDC2 $D203 (53763): audio control 2
AUDF3 $D204 (53764): Audio frequency 3
AUDC3 $D205 (53765): audio control 3
AUDF4 $D206 (53766): Audio frequency 4
AUDC4 $D207 (53767): audio control 4
AUDCTL $D208 (53768): general audio control
STIMER $D209 (53769): audio timer reset
CHAPTER 18
THE JOYSTICK PORTS
The joystick ports are the I/O ports of the PIA chip. This means that
they are bidirectional, capable of output as well as input. The
joystick ports are usually set up for input. To read them, simply
read the port registers. PORTA [$D300 (53016)] will read joystick
ports 1 and 2. PORTB [$D301 (54017)] will read joystick ports 3 and
4. Joystick ports 3 and 4 are used for memory control on the XL/XE
models and don't have external connectors.
Each bit of each port can be configured independently for input or
output. To reconfigure a port, the port control registers, PACTL and
PBCTL [$D302 (54018) and $D303 (54019)], are used. The port control
registers also control some lines on the serial I/O connector.
The port control registers
7 6 5 4 3 2 1 0
PACTL -----------------
or |n 0 1 1 n n 0 n|
PBCTL -----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
bits
PACTL
7 Peripheral A interrupt status. Set by peripheral
interrupt; reset by reading PORTA.
3 Cassette motor control (0 = on: 1 = off).
2 0 = PORTA is now port A direction control.
Writing to PORTA will now set bits for input
or output.
0 sets bit for input; 1 sets bit for output.
1 = PORTA operational
1 1 = peripheral A interrupt enabled.
PBCTL
7 Peripheral B interrupt status. Set by peripheral
interrupt; reset by reading PORTB.
3 Serial connector command line.
2 0 = PORTB is now port B direction control.
Writing to PORTB will now set bits for input
or output.
0 sets bit for input; 1 sets bit for output.
1 = PORTB operational
1 1 = peripheral B interrupt enabled.
The electronic configuration of the controller ports is as follows.
----------- -----------
\0 1 2 3 R/ \4 5 6 7 R/
\t + - L/ \t + - L/
------- -------
0 through 7 are the binary data bits for port A or port B.
+ and - are +5 volts and ground respectively.
R and L are the left and right game paddles.
t is the joystick trigger line.
The data bits in the joystick ports are used as follows for the
joysticks and game paddles.
The joysticks and the port registers
7 6 5 4 3 2 1 0
-----------------
PORTA |U|D|L|R|U|D|L|R|
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
paddle | | | |
triggers 3 2 1 0
PORTB -----------------
(400/800 |U|D|L|R|U|D|L|R|
only) -----------------
paddle | | | |
triggers 7 6 5 4
U = up
D = down
L = left
R = right
The joysticks may be read either directly from the port registers or
from the joystick shadow registers. During vertical blank, the data
in the port registers is separated and put into the shadow registers.
These registers are, STICK0 [$0278 (632)], STICK1 [$0279 (633)],
STICK2 [$027A (634)] and STICK3 [$027B (635)]. The triggers may be
read from the joystick trigger registers, TRIG0 - TRIG3 [$D010 - $D013
(53264 - 53267)]. These register have shadow registers, STRIG0 -
STRIG3 [$0284 - 0287 (644 -647)]. If these registers read zero the
associated triggers are pressed. The paddle triggers may be read from
their shadow registers also. They are, PTRIG0 - PTRIG 7, [$027C -
$0283 (236 - 643)].
THE GAME PADDLE REGISTERS
Although the game paddles are plugged into the joystick ports, they
are not read from the port registers. The game paddles are read by
first writing any number to the start-pot-scan register, POTGO [$D20B
(53771)]]. This turns off the capacitor dump transistors and allows
the pot reading
capacitors to begin charging. It also sets the TV scan line counter
to zero. As each capacitor crosses a certain trigger voltage, the
number of TV lines scanned is put in the respective pot value
register. When the scan counter reaches 228, the capacitor dump
transistors are turned on and the number 228 is put into any pot value
registers which are still empty.
Before reading the pot value registers, ALLPOT [$D208 (53768)] should
be checked. In this register, each bit corresponds to the validity of
a pot value register. If a bit is zero, its' associated pot value
register is valid. If bit 2 of SKCTL, [$D20F (53775)], is 1, the pots
go into the fast scan mode. In this mode the paddles are read in only
2 TV scan lines. They can also be read without regard to POTGO or
ALLPOT.
The pot value registers contain the number of TV scan lines it last
took for the paddle reading capacitors to charge (up to 228). These
registers are POT0 - POT7 [$D200 - $D207 (53760 -53767)]. Their
shadow registers are PADDL0 - PADDL7 [$0270 - $0277 (624 - 631)].
THE LIGHT PEN REGISTERS
Whenever a joystick trigger is pressed, the light pen registers, PENH
and PENV are updated. PENH [$D40C (54284)] takes a value based on a
color clock counter. The value can be from 0 to 227. PENV [$D40D
[54285)] takes the 8 highest bits of the vertical line counter. A
light pen is simply a photo transistor connected to a joystick trigger
line and focused on the TV screen. When the electron beam strikes the
part of the screen the light pen is focused on, the transistor turns
on pulling the trigger line low. The light pen registers then contain
numbers relative to where the light pen was pointing. The shadow
register for PENH and PENV are LPENH [$0234 (564)] and LPENV [$0235
(566)).
Useful operating system equates
TRIG0 $D010 (53264): joystick triggers
|
TRIG3 $D013 (53268):
POT0 $D200 (53760): paddle value
|
POT7 $D207 (53767):
ALLPOT $D208 (53768): reads validity of pot values
POTGO $D20B (53771): starts paddle read
SKCTL $D20F (53775): bit 2 enables fast pot scan
PORTA $D300 (53016): port A data
PORTB $D301 (53017): port B data
PACTL $D302 (54018): port A control
PBCTL $D303 (54019): port B control
PENH $D40C (54284): light pen horizontal value
PENV $D40D (54285): light pen vertical value
Shadow registers
LPENH $0234 (564): light pen horizontal value
LPENV $0235 (566): light pen vertical value
PADDL0 $0270 (624): game paddle values
|
PADDL7 $0277 (631)
STICK0 $0278 (632): joystick registers
|
STICK0 $027B (635):
PRTIG0 $027C (636): paddle triggers
|
PTRIG7 $0283 (643):
STRIG0 $0284 (644): joystick triggers
|
STRIG3 $0287 (647):
CHAPTER 19
MISC HARDWARE REGISTERS AND INFORMATION
VERTICAL LINE COUNTER
The ANTIC chip has a vertical line counter at $0D4B (54283). This
counter shows the high 8 bits of a 9 bit counter. This gives two line
resolution. The value of this counter is placed into PENV [$D40D
(54285)] when a joystick trigger is pressed.
SERIAL PORT REGISTERS
The POKEY chip has some registers which control the serial port.
The serial port control register, SKCTL [$D20F (53775)], controls the
serial port configuration and the game paddle scan mode. and some
keyboard circuitry.
The serial port control register
7 6 5 4 3 2 1 0
-----------------
SKCTL | | | | | | | | |
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
bits
0 1 = enable keyboard debounce
1 1 = enable keyboard scan
both 0 = set initialization mode.
2 1 = fast pot scan
3 1 = serial output is two tone (for cassette)
instead of logical true/false
4\
5 >- serial port mode control
6/
7 1 = forced logical 0 on output
If the serial port control register is read from it gives the serial
port status. The register is then called SKSTAT
Serial port status register
7 6 5 4 3 2 1 0
-----------------
| | | | | | | |1|
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
bits
0 not used, reads 1
1 0 = serial input shift register busy
2 0 = last key is still pressed
3 0 = shift key pressed
4 0 = direct from serial input port
5 0 = keyboard over-run
6 0 = serial data input over-run
7 1 = serial data input frame error
The serial port status is latched and must be reset by writing any
number to its' reset register, SKRES [$D20A (53770)].
SERIAL PORT INPUT AND OUTPUT DATA
When a full byte of serial input data has been received, it is read
from the serial input data register, SERIN [$D20D (53773). Serial
output data is written to the same register, which is then called the
serial output data register, SEROUT. This register is usually written
to in response to a serial output data interrupt (bit 4 of IRQST).
HARDWARE CHIP MEMORY ALLOCATION
The addresses for the hardware chips are not completely decoded. For
example, the PIA needs only four bytes of memory but is active from
$D300 - D3FF. Enough room for 64 PIA chips. A second pair of
parallel ports could be added by accessing the address bus and further
decoding the address for a second PIA. (This would also require a
small modification of the computer's circuit board to disable the
original PIA when the new one is active.) Similarly, there is room
for 15 more POKEY or ANTIC chips and 7 gtia chips, should you ever
need them. (GTIA uses $D000 - D0FF, POKEY uses $D200 - $D2FF and
ANTIC uses $D400 - $D4FF.)
Useful data base variables and OS equates
SKRES $D20A (53770): serial port status reset
SEROUT $D20D (53773): serial output data
SERIN $D20D (53773): serial input data
SKCTL $D20F (53775): serial port control
SKSTAT $D20F (53775): serial port status
VCOUNT $D40B (54283): vertical line counter
Os shadow registers
SSKCTL $0232 (562): SKCTL
CHAPTER 20
THE XL AND XE MODELS
BASIC B BUGS
Most of the Atari 600XL and 800XL models were supplied with the
"debugged" version B of Atari BASIC. This new BASIC got rid of the
minor bugs of BASIC A and introduced some new major bugs of it's own.
Each time a program is saved, 16 extra bytes are tagged onto the end
of the program. After many saves and reloads, as when developing a
long program, the program becomes too large for the memory.
The computer may lock up unpredictably.
Program line links may get messed up, leaving garbage in the listing
and the program unrunable.
Large LISTed programs may not run unless SAVed and reLOADed.
If the length of a listed program is a multiple of a certain number of
bytes, it will not run unless the length is somehow changed.
BASIC version B has been replaced by version C. All of the XE models
have this truly debugged version of BASIC.
NEW OPERATING SYSTEM PROBLEMS
I have heard of only one bug in the operating system in XL and XE
models. This is a mishandling of the printer timeout. The computer
cannot tell if there is a printer attached or not. This may have been
fixed in the XE models. However, many programs, some even formerly
sold by Atari, do not jump through published jump vectors when using
the operating system. These programs will not run on XL/XE models.
(Some of these programs are Atari Word Processor (not Atariwriter) and
LJKs Letter Perfect and Data Perfect.) Since the operating system ROM
can be switched to RAM, a "translator" can be used to load the 800
operating system into an XL or XE model.
130XE MEMORY MANAGEMENT
The 130XE has an extra 64K bank of memory. It is divided into four
blocks of 16K each. Each block can be switched to replace part of the
main bank of RAM from $4000 (16384) to $7FFF (32767). Furthermore, it
can be switched in such a way that only the 6502, or the ANTIC chip
can see the extra memory.
Port B (formerly the two extra joystick ports of the 400/800) is used
to manage the memory.
Port B and memory management
7 6 5 4 3 2 1 0
-----------------
PORTB |T|U|A|C|S S|B|R|
-----------------
1 6 3 1 8 4 2 1
2 4 2 6
8
R 1 = OS replaced by RAM
B 0 = BASIC enabled
S S bank select bits
C 0 = CPU sees switched RAM at $4000
A 0 = ANTIC sees switched RAM
U unused
T 0 = self test
Bits 2 and 3 of PORTB select which block of the extra bank of memory
is switched in.
Bank select bits
bits block
2 3 address
-------------------------
0 0 $0000 - $3FFF
0 1 $4000 - $7FFF
1 0 $8000 - $BFFF
1 1 $C000 - $FFFF
Bits 4 and 5 select which chip sees the switched in RAM at $4000 -
$7FFF
Chip select bits
bits ANTIC 6502
4 5
--------------------------
0 0 Ext. Ext.
0 1 Ext. Main
1 0 Main Ext.
1 1 Main Main
THE XL PARALLEL PORT
Pin out of the parallel port
top from rear
111112222233333444445
2468024680246802468024680
-------------------------
-------------------------
11111222223333344444
1357913579135791357913579
1 2 GND
3 A1 4 A0
5 A3 6 A2
7 A5 8 A4
9 GND 10 A6
11 A8 12 A7
13 A10 14 A9
15 A12 16 A11
17 A14 18 A13
19 A15 20 GND
21 D1 22 D0
23 D3 24 D2
25 D5 26 D4
27 D7 28 D6
29 GND 30 GND
31 GND 32 phase 2 clock
33 RESET 34
35 RDY 36 IRQ
37 37
39 40
41 GND 42
43 RAS 44
45 R/W 46 GND
47 +5V 48 +5V
49 GND 50
The phase 2 clock runs at 1.8 MHz. When the clock is high, the
address and R/W lines are valid. The clock goes from high to low,
when the data lines are also valid. All lines then become invalid.
The 130XE doesn't have the parallel port. However, it has a cartridge
slot expansion. This is a small cartridge-slot-like connector with
the necessary connector to use parallel expansion.
FINE SCROLLING
If address $026E (622) is $FF, graphics 0 will be in the fine scroll
mode.
OTHER ADDRESSES
DSCTLN [$0D25,2 (725)] is the disk sector size. should be $80 (128).
DMASAV [$02DD (735)] is a copy of the DMA control register, SDMCTL
[$022F (559)]. It is set up when a channel is opened to the screen.
The value is moved to SDMCTL whenever a key is pressed. It is used to
restore the display if DMA is disabled.
PUPBT [$033D,3 (829-831)] is used to test memory integrity when
[RESET] is pressed. If these bytes are not $5C, $93 and $25, the
computer will do a cold start when [RESET] is pressed.
The self-test ROM is from $D000 to $D7FF, the same addresses as the
hardware registers. This part of the operating system ROM is disabled
when not used. When The computer is put into the self-test mode, This
part of ROM is copied to $5000 to $57FF and run from there.
GINTLK [$03FA (1018)] is a logical 1 if a cartridge is installed
(built-in BASIC is considered a cartridge). BASIC can be disabled by
poking 1018 with a non-zero number. If [RESET] is then pressed, the
computer will attempt to load the DUP.SYS file and basic will be
completely disabled.
APPENDIX A
HARDWARE REGISTERS
Register Shadow
Name Description Address Name Address
----------------------------------------------------------------------
ALLPOT game paddle ready indicators $D208 53768
AUDC1 Audio channel 1 control $D201 53761
AUDC2 Audio channel 2 control $D203 53763
AUDC3 Audio channel 3 control $D205 53765
AUDC4 Audio channel 1 control $D207 53767
AUDCTL general audio control $D208 53768
AUDF1 Audio frequency 1 control $D200 53760
AUDF2 Audio frequency 2 control $D202 53762
AUDF3 Audio frequency 3 control $D204 53764
AUDF4 Audio frequency 4 control $D206 53766
CHACTL character control $D401 54273 CHART $02F3 755
CHBASE Address of character set / 256 $D409 54281 CHBAS $O2F4 756
COLBK color/brightness of setcolor 4 $D01A 53274 COLOR4 $02C8 712
COLPF0 Color/brightness of setcolor 0 $D016 53270 COLOR0 $02C4 708
COLPF1 color/brightness of setcolor 1 $D017 53271 COLOR1 $02C5 709
COLPF2 color/brightness of setcolor 2 $DO18 53272 COLOR2 $02C6 710
COLPF3 color/brightness of setcolor 3 $DO19 53273 COLOR3 $02C7 711
COLPM0 color/brightness, player/missile 0 $D012 53266 PCOLR0 $02C0 704
COLPM1 color/brightness, player/missile 1 $DO13 53267 PCOLR1 $02C1 705
COLPM2 color/brightness, player/missile 2 $DO14 53268 PCOLR2 $02C2 706
COLPM3 color/brightness, player/missile 3 $DO15 53269 PCOLR3 $02C3 707
CONSOL [START], [SELECT], [OPT.], speaker $D01F 53279
DLISTH display list pointer high byte $D403 54275 SDLSTH $0231 561
DLISTL display list pointer low byte $D402 54274 SDLSTL $0230 560
DMACTL Direct Memory access control (DMA) $D400 54272 SDMCTL $022F 559
GRACTL graphics control $D01D 53277
GRAFM missile graphics $D011 53265
GRAFP0 player 0 graphics $D00D 53261
GRAFP1 player 1 graphics $D00E 53262
GRAFP2 player 2 graphics $D00F 53263
GRAFP3 player 3 graphics $D010 53264
HITCLR clear collisions $D01E 54278
HPOSM0 horizontal position of missile 0 $D004 53252
HPOSM1 horizontal position of missile 1 $D005 53253
HPOSM2 horizontal position of missile 2 $D006 53254
HOPSM3 horizontal position of missile 3 $D007 53255
HPOSP0 horizontal position of player 0 $D000 53248
HPOSP1 horizontal position of player 1 $D001 53249
HPOSP2 horizontal position of player 2 $D002 53250
HPOSP3 horizontal position of player 3 $D003 53251
HSCROL horizontal scroll $D404 54276
IRQEN interrupt request enable (IRQ) $D20E 53774 POKMSK $0010 16
IRQST IRQ status $D20E 53774
KBCODE keyboard code $D209 53769 CH $O2FC 764
M0PF missile 0 to graphics collisions $D000 53248
M0PL missile 0 to player collisions $D008 53256
M1PF missile 1 to graphics collisions $D001 53249
M1PL missile 1 to player collisions $D009 53257
M2PF missile 2 to graphics collisions $D002 53250
M2PL missile 2 to player collisions $D00A 53258
M3PF missile 3 to graphics collisions $D003 53251
M3PL missile 3 to player collisions $D00B 53259
NMIEN non-maskable interrupt enable (NMI)$D40E 54286
NMIRES NMI reset $D40F 54287
NMIST NMI status $D40F 54287
P0PF player 0 to graphics collisions $D004 53252
P0PL player 0 to player collisions $D00C 53260
P1PF player 1 to graphics collisions $D005 53253
P1PL player 1 to player collisions $D00D 53261
P2PF player 2 to graphics collisions $D006 53254
P2PL player 2 to player collisions $D00E 53262
P3PF player 3 to graphics collisions $DOO7 53255
P3PL player 3 to player collisions $D00F 53263
PACTL port A control $D302 54018
PAL Europe/North America TV indicator $D014 53268
PBCLT port B control $D303 54019
PENH light pen horizontal position $D40C 54284 LPENH $0234 564
PENV light pen vertical position $D40D 54285 LPENV $0235 565
PMBASE player/missile address / 256 $D407 54279
PORTA port A $D300 54016 STICK0 $0278 632
STICK1 $0279 634
PORTB port B $D301 54017 STICK2 $027A 634
STICK3 $027B 635
POT0 game paddle 0 $D200 53760 PADDL0 $0270 624
POT1 game paddle 1 $D201 53761 PADDL1 $0271 625
POT2 game paddle 2 $D202 53762 PADDL2 $0272 626
POT3 game paddle 3 $D203 53763 PADDL3 $0273 627
POT4 game paddle 4 $D204 53764 PADDL4 $0274 628
POT5 game paddle 5 $D205 53765 PADDL5 $0275 629
POT6 game paddle 6 $D206 53766 PADDL6 $0276 630
POT7 game paddle 7 $D207 53767 PADDL7 $0277 631
POTGO start pot scan sequence $D20B 53771
PRIOR p/m priority and GTIA mode $D21B 53275 GPRIOR $026F 623
RANDOM random number generator $D20A 53770
SERIN serial port input $D20D 53774
SEROUT serial port output $D20D 53773
SIZEM missile size $D00C 53260
SIZEP0 player 0 size $D008 53256
SIZEP1 player 1 size $D009 53257
SIZEP2 player 2 size $D00A 53258
SIZEP3 player 3 size $D00B 53259
SKCTL serial port control $D20F 53775 SSKCTL $0232 563
SKREST reset serial port status $D20A 53770
SKSTAT serial port status $D20F 53775
STIMER start timer $D209 53769
TRIG0 joystick trigger 0 $D010 53264 STRIG0 $0284 644
TRIG1 joystick trigger 1 $D011 53265 STRIG1 $0285 645
TRIG2 joystick trigger 2 $D012 53266 STRIG2 $0286 646
TRIG3 joystick trigger 3 $D013 53267 STRIG3 $0287 647
VCOUNT vertical line counter $D40B 54283
VDELAY vertical delay $D01C 54276
VSCROL vertical scroll $D405 54277
WSYNC wait for horizontal sync $D40A 54282
NUMERICAL ORDER
Registers sharing addresses are listed first when writen to, then when
read from
Register Shadow
Name Description Address Name Address
----------------------------------------------------------------------
HPOSP0 horizontal position of player 0 $D000 53248
M0PF missile 0 to graphics collisions $D000 53248
HPOSP1 horizontal position of player 1 $D001 53249
M1PF missile 1 to graphics collisions $D001 53249
HPOSP2 horizontal position of player 2 $D002 53250
M2PF missile 2 to graphics collisions $D002 53250
HPOSP3 horizontal position of player 3 $D003 53251
M3PF missile 3 to graphics collisions $D003 53251
HPOSM0 horizontal position of missile 0 $D004 53252
P0PF player 0 to graphics collisions $D004 53252
HPOSM1 horizontal position of missile 1 $D005 53253
P1PF player 1 to graphics collisions $D005 53253
HPOSM2 horizontal position of missile 2 $D006 53254
P2PF player 2 to graphics collisions $D006 53254
HOPSM3 horizontal position of missile 3 $D007 53255
P3PF player 3 to graphics collisions $D007 53255
SIZEP0 player 0 size $D008 53256
M0PL missile 0 to player collisions $D008 53256
SIZEP1 player 1 size $D009 53257
M1PL missile 1 to player collisions $D009 53257
SIZEP2 player 2 size $D00A 53258
M2PL missile 2 to player collisions $D00A 53258
SIZEP3 player 3 size $D00B 53259
M3PL missile 3 to player collisions $D00B 53259
SIZEM missile size $D00C 53260
P0PL player 0 to player collisions $D00C 53260
GRAFP0 player 0 graphics $D00D 53261
P1PL player 1 to player collisions $D00D 53261
GRAFP1 player 1 graphics $D00E 53262
P2PL player 2 to player collisions $D00E 53262
GRAFP2 player 2 graphics $D00F 53263
P3PL player 3 to player collisions $D00F 53263
GRAFP3 player 3 graphics $D010 53264
TRIG0 joystick trigger 0 $D010 53264 STRIG0 $0284 644
GRAFM missile graphics $D011 53265
TRIG1 joystick trigger 1 $D011 53265 STRIG1 $0285 645
COLPM0 color/brightness, player/missile 0 $D012 53266 PCOLR0 $02C0 704
TRIG2 joystick trigger 2 $D012 53266 STRIG2 $0286 646
COLPM1 color/brightness, player/missile 1 $D013 53267 PCOLR1 $02C1 705
TRIG3 joystick trigger 3 $D013 53267 STRIG3 $0287 647
COLPM2 color/brightness, player/missile 2 $D014 53268 PCOLR2 $02C2 706
PAL Europe/North America TV indicator $D014 53268
COLPM3 color/brightness, player/missile 3 $D015 53269 PCOLR3 $02C3 707
COLPF0 Color/brightness of setcolor 0 $D016 53270 COLOR0 $02C4 708
COLPF1 color/brightness of setcolor 1 $D017 53271 COLOR1 $02C5 709
COLPF2 color/brightness of setcolor 2 $D018 53272 COLOR2 $02C6 710
COLPF3 color/brightness of setcolor 3 $D019 53273 COLOR3 $02C7 711
COLBK color/brightness of setcolor 4 $D01A 53274 COLOR4 $02C8 712
VDELAY vertical delay $D01C 54276
GRACTL graphics control $D01D 53277
HITCLR clear collisions $D01E 54278
CONSOL [START], [SELECT], [OPT.], speaker $D01F 53279
AUDF1 Audio frequency 1 control $D200 53760
POT0 game paddle 0 $D200 53760 PADDL0 $0270 624
AUDC1 Audio channel 1 control $D201 53761
POT1 game paddle 1 $D201 53761 PADDL1 $0271 625
AUDF2 Audio frequency 2 control $D202 53762
POT2 game paddle 2 $D202 53762 PADDL2 $0272 626
AUDC2 Audio channel 2 control $D203 53763
POT3 game paddle 3 $D203 53763 PADDL3 $0273 627
AUDF3 Audio frequency 3 control $D204 53764
POT4 game paddle 4 $D204 53764 PADDL4 $0274 628
AUDC3 Audio channel 3 control $D205 53765
POT5 game paddle 5 $D205 53765 PADDL5 $0275 629
AUDF4 Audio frequency 4 control $D206 53766
POT6 game paddle 6 $D206 53766 PADDL6 $0276 630
AUDC4 Audio channel 1 control $D207 53767
POT7 game paddle 7 $D207 53767 PADDL7 $0277 631
ALLPOT game paddle ready indicators $D208 53768
AUDCTL general audio control $D208 53768
KBCODE keyboard code $D209 53769 CH $O2FC 764
STIMER start timer $D209 53769
RANDOM random number generator $D20A 53770
SKREST reset serial port status $D20A 53770
POTGO start pot scan sequence $D20B 53771
SEROUT serial port output $D20D 53773
SERIN serial port input $D20D 53774
IRQEN interrupt request enable (IRQ) $D20E 53774 POKMSK $0010 16
IRQST IRQ status $D20E 53774
SKCTL serial port control $D20F 53775 SSKCTL $0232 563
SKSTAT serial port status $D20F 53775
PRIOR p/m priority and GTIA mode $D21B 53275 GPRIOR $026F 623
PORTA port A $D300 54016 STICK0 $0278 632
STICK1 $0279 633
PORTB port B $D301 54017 STICK2 $027A 634
STICK3 $027B 635
PACTL port A control $D302 54018
PBCTL port B control $D303 54019
DMACTL Direct Memory access control (DMA) $D400 54272 SDMCTL $022F 559
CHACTL character control $D401 54273 CHART $02F3 755
DLISTL display list pointer low byte $D402 54274 SDLSTL $0230 560
DLISTH display list pointer high byte $D403 54275 SDLSTH $0231 561
HSCROL horizontal scroll $D404 54276
VSCROL vertical scroll $D405 54277
PMBASE player/missile address / 256 $D407 54279
CHBASE Address of character set / 256 $D409 54281 CHBAS $O2F4 756
WSYNC wait for horizontal sync $D40A 54282
VCOUNT vertical line counter $D40B 54283
PENH light pen horizontal position $D40C 54284 LPENH $0234 564
PENV light pen vertical position $D40D 54285 LPENV $0235 565
NMIEN non-maskable interrupt enable (NMI)$D40E 54286
NMIRES NMI reset $D40F 54287
NMIST NMI status $D40F 54287
SHADOW REGISTER ORDER
ALPHEBETICAL ORDER
Register Shadow
Name Description Address Name Address
----------------------------------------------------------------------
KBCODE keyboard code $D209 53769 CH $O2FC 764
CHACTL character control $D401 54273 CHART $02F3 755
CHBASE Address of character set / 256 $D409 54281 CHBAS $O2F4 756
COLBK color/brightness of setcolor 4 $D01A 53274 COLOR4 $02C8 712
COLPF0 Color/brightness of setcolor 0 $D016 53270 COLOR0 $02C4 708
COLPF1 color/brightness of setcolor 1 $D017 53271 COLOR1 $02C5 709
COLPF2 color/brightness of setcolor 2 $D018 53272 COLOR2 $02C6 710
COLPF3 color/brightness of setcolor 3 $D019 53273 COLOR3 $02C7 711
PRIOR p/m priority and GTIA mode $D21B 53275 GPRIOR $026F 623
PENH light pen horizontal position $D40C 54284 LPENH $0234 564
PENV light pen vertical position $D40D 54285 LPENV $0235 565
POT0 game paddle 0 $D200 53760 PADDL0 $0270 624
POT1 game paddle 1 $D201 53761 PADDL1 $0271 625
POT2 game paddle 2 $D202 53762 PADDL2 $0272 626
POT3 game paddle 3 $D203 53763 PADDL3 $0273 627
POT4 game paddle 4 $D204 53764 PADDL4 $0274 628
POT5 game paddle 5 $D205 53765 PADDL5 $0275 629
POT6 game paddle 6 $D206 53766 PADDL6 $0276 630
POT7 game paddle 7 $D207 53767 PADDL7 $0277 631
COLPM0 color/brightness, player/missile 0 $D012 53266 PCOLR0 $02C0 704
COLPM1 color/brightness, player/missile 1 $D013 53267 PCOLR1 $02C1 705
COLPM2 color/brightness, player/missile 2 $D014 53268 PCOLR2 $02C2 706
COLPM3 color/brightness, player/missile 3 $D015 53269 PCOLR3 $02C3 707
IRQEN interrupt request enable (IRQ) $D20E 53774 POKMSK $0010 16
DLISTH display list pointer high byte $D403 54275 SDLSTH $0231 561
DLISTL display list pointer low byte $D402 54274 SDLSTL $0230 560
DMACTL Direct Memory access control (DMA) $D400 54272 SDMCTL $022F 559
SKCTL serial port control $D20F 53775 SSKCTL $0232 563
PORTA port A $D300 54016 STICK0 $0278 632
STICK1 $0279 633
PORTB port B $D301 54017 STICK2 $027A 634
STICK3 $027B 635
TRIG0 joystick trigger 0 $D010 53264 STRIG0 $0284 644
TRIG1 joystick trigger 1 $D011 53265 STRIG1 $0285 645
TRIG2 joystick trigger 2 $D012 53266 STRIG2 $0286 646
TRIG3 joystick trigger 3 $D013 53267 STRIG3 $0287 647
NUMERICAL ORDER
IRQEN interrupt request enable (IRQ) $D20E 53774 POKMSK $0010 16
DMACTL Direct Memory access control (DMA) $D400 54272 SDMCTL $022F 559
DLISTL display list pointer low byte $D402 54274 SDLSTL $0230 560
DLISTH display list pointer high byte $D403 54275 SDLSTH $0231 561
SKCTL serial port control $D20F 53775 SSKCTL $0232 563
PENH light pen horizontal position $D40C 54284 LPENH $0234 564
PENV light pen vertical position $D40D 54285 LPENV $0235 565
PRIOR p/m priority and GTIA mode $D21B 53275 GPRIOR $026F 623
POT0 game paddle 0 $D200 53760 PADDL0 $0270 624
POT1 game paddle 1 $D201 53761 PADDL1 $0271 625
POT2 game paddle 2 $D202 53762 PADDL2 $0272 626
POT3 game paddle 3 $D203 53763 PADDL3 $0273 627
POT4 game paddle 4 $D204 53764 PADDL4 $0274 628
POT5 game paddle 5 $D205 53765 PADDL5 $0275 629
POT6 game paddle 6 $D206 53766 PADDL6 $0276 630
POT7 game paddle 7 $D207 53767 PADDL7 $0277 631
PORTA port A $D300 54016 STICK0 $0278 632
STICK1 $0279 633
PORTB port B $D301 54017 STICK2 $027A 634
STICK3 $027B 635
TRIG0 joystick trigger 0 $D010 53264 STRIG0 $0284 644
TRIG1 joystick trigger 1 $D011 53265 STRIG1 $0285 645
TRIG2 joystick trigger 2 $D012 53266 STRIG2 $0286 646
TRIG3 joystick trigger 3 $D013 53267 STRIG3 $0287 647
COLPM0 color/brightness, player/missile 0 $D012 53266 PCOLR0 $02C0 704
COLPM1 color/brightness, player/missile 1 $D013 53267 PCOLR1 $02C1 705
COLPM2 color/brightness, player/missile 2 $D014 53268 PCOLR2 $02C2 706
COLPM3 color/brightness, player/missile 3 $D015 53269 PCOLR3 $02C3 707
COLPF0 Color/brightness of setcolor 0 $D016 53270 COLOR0 $02C4 708
COLPF1 color/brightness of setcolor 1 $D017 53271 COLOR1 $02C5 709
COLPF2 color/brightness of setcolor 2 $D018 53272 COLOR2 $02C6 710
COLPF3 color/brightness of setcolor 3 $D019 53273 COLOR3 $02C7 711
COLBK color/brightness of setcolor 4 $D01A 53274 COLOR4 $02C8 712
CHACTL character control $D401 54273 CHART $02F3 755
CHBASE Address of character set / 256 $D409 54281 CHBAS $O2F4 756
KBCODE keyboard code $D209 53769 CH $O2FC 764
APPENDIX B
OPERATING SYSTEM EQUATES
0100 ;
0101 ; ATARI 800 EQUATE LISTING
0102 ;
0103 ;
0104 ;
0105 ;This listing is based on the original release of Operating System,
0106 ;version A. The vectors shown here were not changed in version B.
0107 ;New equates for XL and XE models are included and noted. Changes
0108 ;from version B to XL/XE are also noted.
0109 ;
0110 ;Most of the equate names given below are the official Atari
0111 ;names. They are in common use but are not mandatory.
0112 ;
0113 ;
0114 ; DEVICE NAMES
0115 ;
0116 ;
0117 ;SCREDT = "E" SCREEN EDITOR
0118 ;KBD = "K" KEYBOARD
0119 ;DISPLY = "S" DISPLAY
0120 ;PRINTR = "P" PRINTER
0121 ;CASSET = "C" CASSETTE
0122 ;DISK = "D" DISK DRIVE
0123 ;
0124 ;
0125 ;
0126 ; STATUS CODES
0127 ;
0128 ;
0129 SUCCES = $01 1
0130 BRKABT = $80 128 BREAK KEY ABORT
0131 PRVOPN = $82 130 IOCB ALREADY OPEN
0132 NONDEV = $82 130 NONEXISTANT DEVICE
0133 WRONLY = $83 131 OPENED FOR WRITE ONLY
0134 NVALID = $84 132 INVALID COMMAND
0135 NOTOPN = $85 133 DEVICE OR FILE NOT OPEN
0136 BADIOC = $86 134 INVALID IOCB NUMBER
0137 RDONLY = $87 135 OPENED FOR READ ONLY
0138 EOFERR = $88 136 END OF FILE
0139 TRNRCD = $89 137 TRUNCATED RECORD
0140 TIMOUT = $8A 138 PERIPHERAL TIME OUT
0141 DNACK = $8B 139 DEVICE DOES NOT ACKNOWLEDGE
0142 FRMERR = $8C 140 SERIAL BUS FRAMING ERROR
0143 CRSROR = $8D 141 CURSOR OUT OF RANGE
0144 OVRRUN = $8E 142 SERIAL BUS DATA OVERRUN
0145 CHKERR = $8F 143 SERIAL BUS CHECKSUM ERROR
0146 DERROR = $90 144 PERIPHERAL DEVICE ERROR
0147 BADMOD = $91 145 NON EXISTANT SCREEN MODE
0148 FNCNOT = $92 146 FUNCTION NOT IMPLEMENTED
0149 SCRMEM = $93 147 NOT ENOUGH MEMORY FOR SCREEN MODE
0150 ;
0151 ;
0152 ;
0153 ;
0154 ; COMMAND CODES FOR CIO
0155 ;
0156 ;
0157 OPEN = $03 3
0158 OPREAD = $04 4 OPEN FOR INPUT
0159 GETREC = $05 5 GET RECORD
0160 OPDIR = $06 6 OPEN TO DISK DIRECTORY
0161 GETCHR = $07 7 GET BYTE
0162 OWRITE = $08 8 OPEN FOR OUTPUT
0163 PUTREC = $09 9 WRITE RECORD
0164 APPEND = $09 9 OPEN TO APPEND TO END OF DISK FILE
0165 MXDMOD = $10 16 OPEN TO SPLIT SCREEN (MIXED MODE)
0166 PUTCHR = $0B 11 PUT-BYTE
0167 CLOSE = $0C 12
0168 OUPDAT = $0C 12 OPEN FOR INPUT AND OUTPUT AT THE SAME TIME
0169 STATUS = $0D 13
0170 SPECIL = $0E 14 BEGINNING OF SPECIAL COMMANDS
0171 DRAWLN = $11 17 SCREEN DRAW
0172 FILLIN = $12 18 SCREEN FILL
0173 RENAME = $20 32
0174 INSCLR = $20 32 OPEN TO SCREEN BUT DON'T ERASE
0175 DELETE = $21 33
0176 DFRMAT = $21 33 FORMAT DISK (RESIDENT DISK HANDLER (RDH))
0177 LOCK = $23 35
0178 UNLOCK = $24 36
0179 POINT = $25 37
0180 NOTE = $26 38
0181 PTSECT = $50 80 RDH PUT SECTOR
0182 GTSECT = $52 82 RDH GET SECTOR
0183 DSTAT = $53 83 RDH GET STATUS
0184 PSECTV = $57 87 RDH PUT SECTOR AND VERIFY
0185 NOIRG = $80 128 NO GAP CASSETTE MODE
0186 CR = $9B 155 CARRIAGE RETURN (EOL)
0187 ;
0188 IOCBSZ = $10 16 IOCB SIZE
0189 MAXIOC = $80 128 MAX IOCB BLOCK SIZE
0190 IOCBF = $FF 255 IOCB FREE
0191 ;
0192 LEDGE = $02 2 DEFAULT LEFT MARGIN
0193 REDGE = $27 39 DEFAULT RIGHT MARGIN
0194 ;
0195 ; OS VARIABLES
0196 ;
0197 ; PAGE 0
0198 ;
0199 LINZBS = $00 0 (800) FOR ORIGINAL DEBUGGER
0200 ; $00 0 (XL) RESERVED
0201 NGFLAG = $01 1 (XL) FOR POWER-UP SELF TEST
0202 CASINI = $02 2
0203 RAMLO = $04 4 POINTER FOR SELF TEST
0204 TRAMSZ = $06 6 TEMPORARY RAM SIZE
0205 TSTDAT = $07 7 TEST DATA
0206 WARMST = $08 8
0207 BOOT? = $09 9 SUCCESSFUL BOOT FLAG
0208 DOSVEC = $0A 10 PROGRAM RUN VECTOR
0209 DOSINI = $0C 12 PROGRAM INITIALIZATION
0210 APPMHI = $0E 14 DISPLAY LOW LIMIT
0211 POKMSK = $10 16 IRQ ENABLE FLAGS
0212 BRKKEY = $11 17 FLAG
0213 RTCLOK = $12 18 3 BYTES, MSB FIRST
0214 BUFADR = $15 21 INDIRECT BUFFER ADDRESS
0215 ICCOMT = $17 23 COMMAND FOR VECTOR
0216 DSKFMS = $18 24 DISK FILE MANAGER POINTER
0217 DSKUTL = $1A 26 DISK UTILITY POINTER (DUP.SYS)
0218 PTIMOT = $1C 28 (800) PRINTER TIME OUT REGISTER
0219 ABUFPT = $1C 28 (XL) RESERVED
0220 PBPNT = $1D 29 (800) PRINTER BUFFER POINTER
0221 ; $1D 29 (XL) RESERVED
0222 PBUFSZ = $1E 30 (800) PRINTER BUFFER SIZE
0223 ; $1E 30 (XL) RESERVED
0224 PTEMP = $1F 31 (800) TEMPORARY REGISTER
0225 ; $1F 31 (XL) RESERVED
0226 ZIOCB = $20 32 ZERO PAGE IOCB
0227 ICHIDZ = $20 32 HANDLER INDEX NUMBER (ID)
0228 ICDNOZ = $21 33 DEVICE NUMBER
0229 ICCOMZ = $22 34 COMMAND
0230 ICSTAZ = $23 35 STATUS
0231 ICBALZ = $24 36 BUFFER POINTER LOW BYTE
0232 ICBAHZ = $25 37 BUFFER POINTER HIGH BYTE
0233 ICPTLZ = $26 38 PUT ROUTINE POINTER LOW
0234 ICPTHZ = $27 39 PUT ROUTINE POINTER HIGH
0235 ICBLLZ = $28 40 BUFFER LENGTH LOW
0236 ICBLHZ = $29 41
0237 ICAX1Z = $2A 42 AUXILIARY INFORMATION BYTE 1
0238 ICAX2Z = $2B 43
0239 ICSPRZ = $2C 44 TWO SPARE BYTES (CIO USE)
0240 ICIDNO = $2E 46 IOCB NUMBER X 16
0241 CIOCHR = $2F 47 CHARACTER BYTE FOR CURRENT OPERATION
0242 ;
0243 STATUS = $30 48 STATUS STORAGE
0244 CHKSUM = $31 49 SUM WITH CARRY ADDED BACK
0245 BUFRLO = $32 50 DATA BUFFER LOW BYTE
0246 BUFRHI = $33 51
0247 BFENLO = $34 52 ADDRESS OF LAST BUFFER BYTE +1 (LOW)
0248 BFENHI = $35 53
0249 CRETRY = $36 54 (800) NUMBER OF COMMAND FRAME RETRIES
0250 LTEMP = $36 54 (XL) LOADER TEMPORARY STORAGE, 2 BYTES
0251 DRETRY = $37 55 (800) DEVICE RETRIES
0252 BUFRFL = $38 56 BUFFER FULL FLAG
0253 RECVDN = $39 57 RECEIVE DONE FLAG
0254 XMTDON = $3A 58 TRANSMISSION DONE FLAG
0255 CHKSNT = $3B 59 CHECKSUM-SENT FLAG
0256 NOCKSM = $3C 60 CHECKSUM-DOES-NOT-FOLLOW-DATA FLAG
0257 BPTR = $3D 61
0258 FTYPE = $3E 62
0259 FEOF = $3F 63
0260 FREQ = $40 64
0261 ;
0262 SOUNDR = $41 65 0=QUIET I/O
0263 CRITIC = $42 66 CRITICAL FUNCTION FLAG, NO DEFFERED VBI
0264 FMSZPG = $43 67 DOS ZERO PAGE, 7 BYTES
0265 CKEY = $4A 74 (800) START KEY FLAG
0266 ZCHAIN = $4A 74 (XL) HANDLER LOADER TEMP, 2 BYTES
0267 CASSBT = $4B 75 (800) CASSETTE BOOT FLAG
0268 DSTAT = $4C 76 DISPLAY STATUS
0269 ;
0270 ATRACT = $4D 77
0271 DRKMSK = $4E 78 ATTRACT MASK
0272 COLRSH = $4F 79 ATTRACT COLOR SHIFTER (EORed WITH
GRAPHICS)
0273 ;
0274 TMPCHR = $50 80
0275 HOLD1 = $51 81
0276 LMARGN = $52 82 SCREEN LEFT MARGIN REGISTER
0277 RMARGN = $53 83 SCREEN RIGHT MARGIN
0278 ROWCRS = $54 84 CURSOR ROW
0279 COLCRS = $55 85 CURSOR COLUMN, 2 BYTES
0280 DINDEX = $57 87 DISPLAY MODE
0281 SAVMSC = $58 88 SCREEN ADDRESS
0282 OLDROW = $5A 90 CURSOR BEFORE DRAW OR FILL
0283 OLDCOL = $5B 91
0284 OLDCHR = $5D 93 DATA UNDER CURSOR
0285 OLDADR = $5E 94 CURSOR ADDRESS
0286 NEWROW = $60 96 (800) DRAWTO DESTINATION
0287 FKDEF = $60 96 (XL) FUNCTION KEY DEFINATION POINTER
0288 NEWCOL = $61 97 (800) DRAWTO DESTINATION, 2 BYTES
0289 PALNTS = $62 98 (XL) EUROPE/NORTH AMERICA TV FLAG
0290 LOGCOL = $63 99 LOGICAL LINE COLUMN POINTER
0291 MLTTMP = $66 102
0292 OPNTMP = $66 102 TEMPORARY STORAGE FOR CHANNEL OPEN
0293 SAVADR = $68 104
0294 RAMTOP = $6A 106 START OF ROM (END OF RAM + 1), HIGH BYTE
ONLY
0295 BUFCNT = $6B 107 BUFFER COUNT
0296 BUFSTR = $6C 108 POINTER USED BY EDITOR
0297 BITMSK = $6E 110 POINTER USED BY EDITOR
0298 SHFAMT = $6F 111
0299 ROWAC = $70 112
0300 COLAC = $72 114
0301 ENDPT = $74 116
0302 DELTAR = $76 118
0303 DELTAC = $77 119
0304 ROWINC = $79 121 (800)
0305 KEYDEF = $79 121 (XL) KEY DEFINATION POINTER, 2 BYTES
0306 COLINC = $7A 122 (800)
0307 SWPFLG = $7B 123 NON 0 IF TEXT AND REGULAR RAM IS SWAPPED
0308 HOLDCH = $7C 124 CH MOVED HERE BEFORE CTRL AND SHIFT
0309 INSDAT = $7D 125
0310 COUNTR = $7E 126
0311 ;
0312 ZROFRE = $80 128 FREE ZERO PAGE, 84 BYTES
0313 FPZRO = $D4 212 FLOATING POINT RAM, 43 BYTES
0314 FR0 = $D4 212 FP REGISTER 0
0315 FRE = $DA 218
0316 FR1 = $E0 224 FP REGISTER 1
0317 FR2 = $E6 230 FP REGISTER 2
0318 FRX = $EC 236 SPARE
0319 EEXP = $ED 237 VALUE OF E
0320 NSIGN = $ED 237 SIGN OF FP NUMBER
0321 ESIGN = $EF 239 SIGN OF FP EXPONENT
0322 FCHFLG = $F0 240 FIRST CHARACTER FLAG
0323 DIGRT = $F1 241 NUMBER OF DIGITS RIGHT OF DECIMAL POINT
0324 CIX = $F2 242 INPUT INDEX
0325 INBUFF = $F3 243 POINTER TO ASCII FP NUMBER
0326 ZTEMP1 = $F5 245
0327 ZTEMP4 = $F7 247
0328 ZTEMP3 = $F9 249
0329 DEGFLG = $FB 251
0330 RADFLG = $FB 251 0=RADIANS, 6=DEGREES
0331 FLPTR = $FC 252 POINTER TO BCD FP NUMBER
0332 FPTR2 = $FE 254
0333 ;
0334 ;
0335 ; PAGE 1
0336 ;
0337 ; 65O2 STACK
0338 ;
0339 ;
0340 ;
0341 ;
0342 ; PAGE 2
0343 ;
0344 ;
0345 INTABS = $0200 512 INTERRUPT RAM
0346 VDSLST = $0200 512 NMI VECTOR
0347 VPRCED = $0202 514 PROCEED LINE IRQ VECTOR
0348 VINTER = $0204 516 INTERRUPT LINE IRQ VECTOR
0349 VBREAK = $0206 518
0350 VKEYBD = $0208 520
0351 VSERIN = $020A 522 SERIAL INPUT READY IRQ
0352 VSEROR = $020C 524 SERIAL OUTPUT READY IRQ
0353 VSEROC = $020E 526 SERIAL OUTPUT COMPLETE IRQ
0354 VTIMR1 = $0210 528 TIMER 1 IRQ
0355 VTIMR2 = $0212 530 TIMER 2 IRQ
0356 VTIMR4 = $0214 532 TIMER 4 IRQ
0357 VIMIRQ = $0216 534 IRQ VECTOR
0358 CDTMV1 = $0218 536 DOWN TIMER 1
0359 CDTMV2 = $021A 538 DOWN TIMER 2
0360 CDTMV3 = $021C 540 DOWN TIMER 3
0361 CDTMV4 = $021E 542 DOWN TIMER 4
0362 CDTMV5 = $0220 544 DOWN TIMER 5
0363 VVBLKI = $0222 546
0364 VVBLKD = $0224 548
0365 CDTMA1 = $0226 550 DOWN TIMER 1 JSR ADDRESS
0366 CDTMA2 = $0228 552 DOWN TIMER 2 JSR ADDRESS
0367 CDTMF3 = $022A 554 DOWN TIMER 3 FLAG
0368 SRTIMR = $022B 555 REPEAT TIMER
0369 CDTMF4 = $022C 556 DOWN TIMER 4 FLAG
0370 INTEMP = $022D 557 IAN'S TEMP
0371 CDTMF5 = $022E 558 DOWN TIMER FLAG 5
0372 SDMCTL = $022F 559 DMACTL SHADOW
0373 SDLSTL = $0230 560 DISPLAY LIST POINTER
0374 SSKCTL = $0232 562 SKCTL SHADOW
0375 ; $0233 563 (800) UNLISTED
0376 LCOUNT = $0233 563 (XL) LOADER TEMP
0377 LPENH = $0234 564 LIGHT PEN HORIZONTAL
0378 LPENV = $0235 565 LIGHT PEN VERTICAL
0379 ; $0236 566 2 SPARE BYTES
0380 ; $0238 568 (800) SPARE, 2 BYTES
0381 RELADR = $0238 568 (XL) LOADER
0382 CDEVIC = $023A 570 DEVICE COMMAND FRAME BUFFER
0383 CAUX1 = $023C 572 DEVICE COMMAND AUX 1
0384 CAUX2 = $023D 573 DEVICE COMMAND AUX 2
0385 TEMP = $023E 574 TEMPORARY STORAGE
0386 ERRFLG = $023F 575 DEVICE ERROR FLAG (EXCEPT TIMEOUT)
0387 DFLAGS = $0240 576 FLAGS FROM DISK SECTOR 1
0388 DBSECT = $0241 577 NUMBER OF BOOT DISK SECTORS
0389 BOOTAD = $0242 578 BOOT LOAD ADDRESS POINTER
0390 COLDST = $0244 580 COLD START FLAG, 1 = COLD START IN
PROGRESS
0391 ; $0245 581 (800) SPARE
0392 RECLEN = $0245 581 (XL) LOADER
0393 DSKTIM = $0246 582 (800) DISK TIME OUT REGISTER
0394 ; $0246 582 (XL) RESERVED, 39 BYTES
0395 LINBUF = $0247 583 (800) CHARACTER LINE BUFFER, 40 BYTES
0396 CHSALT = $026B 619 (XL) CHARACTER SET POINTER
0397 VSFLAG = $026C 620 (XL) FINE SCROLL TEMPORARY
0398 KEYDIS = $026D 621 (XL) KEYBOARD DISABLE
0399 FINE = $026E 622 (XL) FINE SCROLL FLAG
0400 GPRIOR = $026F 623 P/M PRIORITY AND GTIA MODES
0401 GTIA = $026F 623
0402 PADDL0 = $0270 624 (XL) 3 MORE PADDLES, (800) 6 MORE PADDLES
0403 STICK0 = $0278 632 (XL) 1 MORE STICK, (800) 3 MORE STICKS
0404 PTRIG0 = $027C 636 (XL) 3 MORE PADDLE TRIGGERS, (800) 6 MORE
0405 STRIG0 = $0284 644 (XL) 1 MORE STICK TRIGGER, (800) 3 MORE
0406 CSTAT = $0288 648 (800)
0407 WMODE = $0289 649
0408 BLIM = $028A 650
0409 ; $028B 651 5 SPARE BYTES
0410 NEWADR = $028E 654 (XL) LOADER RAM
0411 TXTROW = $0290 656
0412 TXTCOL = $0291 657
0413 TINDEX = $0293 659 TEXT INDEX
0414 TXTMSC = $0294 660
0415 TXTOLD = $0296 662 OLD ROW AND OLD COL FOR TEXT, 2 BYTES
0416 ; $0298 664 4 SPARE BYTES
0417 TMPX1 = $029C 668 (800)
0418 CRETRY = $029C 668 (XL) NUMBER OF COMMAND FRAME RETRIES
0419 SUBTMP = $029E 670
0420 HOLD2 = $029F 671
0421 DMASK = $02A0 672
0422 TMPLBT = $02A1 673
0423 ESCFLG = $02A2 674
0424 TABMAP = $02A3 675 15 BYTE BIT MAP FOR TAB SETTINGS
0425 LOGMAP = $02B2 690 4 BYTE LOGICAL LINE START BIT MAP
0426 INVFLG = $02B6 694
0427 FILFLG = $02B7 695 FILL DIRING DRAW FLAG
0428 TMPROW = $02B8 696
0429 TMPCOL = $02B9 697
0430 SCRFLG = $02BB 699 SCROLL FLAG
0431 HOLD4 = $02BC 700
0432 HOLD5 = $02BD 701 (800)
0433 DRETRY = $02BD 701 (XL) NUMBER OF DEVICE RETRIES
0434 SHFLOC = $02BE 702
0435 BOTSCR = $02BF 703 24 NORM, 4 SPLIT
0436 PCOLR0 = $02C0 704 3 MORE PLAYER COLOR REGISTERS
0437 COLOR0 = $02C4 708 4 MORE GRAPHICS COLOR REGISTERS
0438 ; $02C9 713 (800) 23 SPARE BYTES
0439 RUNADR = $02C9 713 (XL) LOADER VECTOR
0440 HIUSED = $02CB 715 (XL) LOADER VECTOR
0441 ZHIUSE = $02CD 717 (XL) LOADER VECTOR
0442 GBYTEA = $02CF 719 (XL) LOADER VECTOR
0443 LOADAD = $02D1 721 (XL) LOADER VECTOR
0444 ZLOADA = $02D3 723 (XL) LOADER VECTOR
0445 DSCTLN = $02D5 725 (XL) DISK SECTOR SIZ
0446 ACMISR = $02D7 727 (XL) RESERVED
0447 KRPDER = $02D9 729 (XL) KEY AUTO REPEAT DELAY
0448 KEYREP = $02DA 730 (XL) KEY AUTO REPEAT RATE
0449 NOCLIK = $02DB 731 (XL) KEY CLICK DISABLE
0450 HELPFG = $02DC 732 (XL) HELP KEY FLAG
0451 DMASAV = $02DD 733 (XL) SDMCTL (DMA) SAVE
0452 PBPNT = $02DE 734 (XL) PRINTER BUFFER POINTER
0453 PBUFSZ = $02DF 735 (XL) PRINTER BUFFER SIZE
0454 GLBABS = $02E0 736 GLOBAL VARIABLES, 4 SPARE BYTES
0455 RAMSIZ = $02E4 740 PERMANENT START OF ROM POINTER
0456 MEMTOP = $02E5 741 END OF FREE RAM
0457 MEMLO = $02E7 743
0458 ; $02E9 745 (800) SPARE
0459 HNDLOD = $02E9 745 (XL) HANDLER LOADER FLAG
0460 DVSTAT = $02EA 746 DEVICE STATUS BUFFER, 4 BYTES
0461 CBAUDL = $02EE 750 CASSETTE BAUD RATE, 2 BYTES
0462 CRSINH = $02F0 752 1 = INHIBIT CURSOR
0463 KEYDEL = $02F1 753 KEY DELAY AND RATE
0464 CH1 = $02F2 754
0465 CHACT = $02F3 755
0466 CHBAS = $02F4 756 CHARACTER SET POINTER
0467 NEWROW = $02F5 757 (XL) DRAW DESTINATION
0468 NEWCOL = $02F6 758 (XL) DRAW DESTINATION
0469 ROWINC = $02F8 760 (XL)
0470 COLINC = $02F9 761 (XL)
0471 CHAR = $02FA 762
0472 ATACHR = $02FB 763 ATASCII CHARACTER FOR CIO
0473 CH = $02FC 764
0474 FILDAT = $02FC 764 COLOR FOR SCREEN FILL
0475 DSPFLG = $02FE 766 DISPLAY CONTROL CHARACTERS FLAG
0476 SSFLAG = $02FF 767 DISPLAY START/STOP FLAFG
0477 ;
0478 ;
0479 ; PAGE 3
0480 ;
0481 ;
0482 ; RESIDENT DISK HANDLER/SIO INTERFACE
0483 ;
0484 DCB = $0300 768 DEVICE CONTROL BLOCK
0485 DDEVIC = $0300 768
0486 DUNIT = $0301 769
0487 DCOMND = $0302 770
0488 DSTATS = $0303 771
0489 DBUFLO = $0304 772
0490 DBUFHI = $0305 773
0491 DTIMLO = $0306 774
0492 DBYTLO = $0308 776
0493 DBYTHI = $0309 777
0494 DAUX1 = $030A 778
0495 DAUX2 = $030B 779
0496 TIMER1 = $030C 780 INITIAL TIMER VALUE
0497 ADDCOR = $030E 782 (800) ADDITION CORRECTION
0498 JMPERS = $030E 782 (XL) OPTION JUMPERS
0499 CASFLG = $030F 783 CASSETTE MODE WHEN SET
0500 TIMER2 = $0310 784 FINAL VALUE, TIMERS 1 & 2 DETERMINE BAUD
RATE
0501 TEMP1 = $0312 786
0502 TEMP2 = $0313 787 (XL)
0503 TEMP2 = $0314 788 (800)
0504 PTIMOT = $0314 788 (XL) PRINTER TIME OUT
0505 TEMP3 = $0315 789
0506 SAVIO = $0316 790 SAVE SERIAL IN DATA PORT
0507 TIMFLG = $0317 791 TIME OUT FLAG FOR BAUD RATE CORRECTION
0508 STACKP = $0318 792 SIO STACK POINTER SAVE
0509 TSTAT = $0319 793 TEMPORARY STATUS HOLDER
0510 HATABS = $031A 794 HANDLER ADDRESS TABLE, 38 BYTES
0511 MAXDEV = $0321 801 MAXIMUM HANDLER ADDRESS INDEX
0512 PUPBT1 = $033D 829 (XL) POWER-UP/RESET
0513 PUPBT2 = $033E 830 (XL) POWER-UP/RESET
0514 PUPBT3 = $033F 831 (XL) POWER-UP/RESET
0515 ;
0516 ;IOCB's
0517 ;
0518 IOCB = $0340 832
0519 ICHID = $0340 832
0520 ICDNO = $0341 833
0521 ICCOM = $0342 834
0522 ICSTA = $0343 835
0523 ICBAL = $0344 836
0524 ICBAH = $0345 837
0525 ICPTL = $0346 838
0526 ICPTH = $0347 839
0527 ICBLL = $0348 840
0528 ICBLH = $0349 841
0529 ICAX1 = $034A 842
0530 ICAX2 = $034B 843
0531 ICAX3 = $034C 844
0532 ICAX4 = $034D 845
0533 ICAX5 = $034E 846
0534 ICAX6 = $034F 847
0535 ; OTHER IOCB's, 112 BYTES
0536 PRNBUF = $03C0 960 PRINTER BUFFER, 40 BYTES
0537 ; $03E8 1000 (800) 21 SPARE BYTES
0538 SUPERF = $03E8 1000 (XL) SCREEN EDITOR
0539 CKEY = $03E9 1001 (XL) START KEY FLAG
0540 CASSBT = $03EA 1002 (XL) CASSETTE BOOT FLAG
0541 CARTCK = $03EB 1003 (XL) CARTRIDGE CHECKSUM
0542 ACMVAR = $03ED 1005 (XL) RESERVED, 6 BYTES
0543 MINTLK = $03F9 1017 (XL) RESERVED
0544 GINTLK = $03FA 1018 (XL) CARTRIDGE INTERLOCK
0545 CHLINK = $03FB 1019 (XL) HANDLER CHAIN, 2 BYTES
0546 CASBUF = $03FD 1021 CASSETTE BUFFER, 131 BYTES TO $047F
0547 ;
0548 ;
0549 ; PAGE 4
0550 ;
0551 ;
0552 USAREA = $0480 1152 128 SPARE BYTES
0553 ;
0554 ; SEE APPENDIX C FOR PAGES 4 AND 5 USAGE
0555 ;
0556 ;
0557 ;
0558 ;
0559 ; PAGE 5
0560 ;
0561 PAGE5 = $0500 1280 127 FREE BYTES
0562 ; $057E 1406 129 FREE BYTES IF FLOATING POINT ROUTINES
NOT USED
0563 ;
0564 ;FLOATING POINT NON-ZERO PAGE RAM, NEEDED ONLY IF FP IS USED
0565 ;
0566 LBPR1 = $057E 1406 LBUFF PREFIX 1
0567 LBPR2 = $05FE 1534 LBUFF PREFIX 2
0568 LBUFF = $0580 1408 LINE BUFFER
0569 PLYARG = $05E0 1504 POLYNOMIAL ARGUMENTS
0570 FPSCR = $05E6 1510 PLYARG+FPREC
0571 FPSCR1 = $05EC 1516 FPSCR+FPREC
0572 FSCR = $05E6 1510 =FPSCR
0573 FSCR1 = $05EC 1516 =FPSCR1
0574 LBFEND = $05FF 1535 END OF LBUFF
0575 ;
0576 ;
0577 ; PAGE 6
0578 ;
0579 ;
0580 PAGE6 = $0600 1536 256 FREE BYTES
0581 ;
0582 ;
0583 ; PAGE 7
0584 ;
0585 ;
0586 BOOTRG = $0700 1792 PROGRAM AREA
0587 ;
0588 ;
0589 ; UPPER ADDRESSES
0590 ;
0591 ;
0592 RITCAR = $8000 32768 RAM IF NO CARTRIDGE
0593 LFTCAR = $A000 40960 RAM IF NO CARTRIDGE
0594 C0PAGE = $C000 49152 (800) EMPTY, 4K BYTES
0595 C0PAGE = $C000 49152 (XL) 2K FREE RAM IF NO CARTRIDGE
0596 ; $C800 51200 (XL) START OF OS ROM
0597 CHORG2 = $CC00 52224 (XL) INTERNATIONAL CHARACTER SET
0598 ;
0599 ;
0600 ; HARDWARE REGISTERS
0601 ;
0602 ;
0603 ; SEE REGISTER LIST FOR MORE INFORMATION
0604 ;
0605 ;
0606 HPOSP0 = $D000 53248
0607 M0PF = $D000 53248
0608 SIZEP0 = $D008 53256
0609 M0PL = $D008 53256
0610 SIZEM = $D00C 53260
0611 GRAFP0 = $D00D 53261
0612 GRAFM = $D011 53265
0613 COLPM0 = $D012 53266
0614 COLPF0 = $D016 53270
0615 PRIOR = $D01B 53275
0616 GTIAR = $D01B 53275
0617 VDELAY = $D01C 53276
0618 GRACTL = $D01D 53277
0619 HITCLR = $D01E 53278
0620 CONSOL = $D01F 53279
0621 AUDF1 = $D200 53760
0622 AUDC1 = $D201 53761
0623 AUDCTL = $D208 53768
0624 RANDOM = $D20A 53770
0625 IRQEN = $D20E 53774
0626 SKCTL = $D20F 53775
0627 PORTA = $D300 54016
0628 PORTB = $D301 54017
0629 PACTL = $D302 54018
0630 PBCTL = $D303 54019
0631 DMACLT = $D400 54272
0632 DLISTL = $D402 54274
0633 HSCROL = $D404 54276
0634 VSCROL = $D405 54277
0635 CHBASE = $D409 54281
0636 WSYNC = $D40A 54282
0637 VCOUNT = $D40B 54283
0638 NMIEN = $D40E 54286
0639 ;
0640 ; FLOATING POINT MATH ROUTINES
0641 ;
0642 AFP = $D800 55296
0643 FASC = $D8E6 55526
0644 IFP = $D9AA 55722
0645 FPI = $D9D2 55762
0646 ZFR0 = $DA44 55876
0647 ZF1 = $DA46 55878
0648 FSUB = $DA60 55904
0649 FADD = $DA66 55910
0650 FMUL = $DADB 56027
0651 FDIV = $DB28 56104
0652 PLYEVL = $DD40 56640
0653 FLD0R = $DD89 56713
0654 FLD0P = $DD8D 56717
0655 FLD1R = $DD98 56728
0656 FLD1P = $DD9C 56732
0657 FSTOR = $DDA7 56743
0658 FSTOP = $DDAB 56747
0659 FMOVE = $DDB6 56758
0660 EXP = $DDC0 56768
0661 EXP10 = $DDCC 56780
0662 LOG = $DECD 57037
0663 LOG10 = $DED1 57041
0664 ;
0665 ;
0666 ; OPERATING SYSTEM
0667 ;
0668 ;
0669 ; MODULE ORIGIN TABLE
0670 ;
0671 CHORG = $E000 57344 CHARACTER SET, 1K
0672 VECTBL = $E400 58368 VECTOR TABLE
0673 VCTABL = $E480 58496 RAM VECTOR INITIAL VALUE TABLE
0674 CIOORG = $E4A6 58534 CIO HANDLER
0675 INTORG = $E6D5 59093 INTERRUPT HANDLER
0676 SIOORG = $E944 59716 SIO DRIVER
0677 DSKORT = $EDEA 60906 DISK HANDLER
0678 PRNORG = $EE78 61048 PRINTER HANDLER
0679 CASORG = $EE78 61048 CASSETTE HANDLER
0680 MONORG = $F0E3 61667 MONITOR/POWER UP MODULE
0681 KBDORG = $F3E4 62436 KEYBOARD/DISPLAY HANDLER
0682 ;
0683 ;
0684 ; VECTOR TABLE, CONTAINS ADDRESSES OF CIO ROUTINES IN THE
0685 ; FOLLOWING ORDER. THE ADDRESSES IN THE TABLE ARE TRUE ADDRESSES-1
0686 ;
0687 ; ADDRESS + 0 OPEN
0688 ; + 2 CLOSE
0689 ; + 4 GET
0690 ; + 6 PUT
0691 ; + 8 STATUS
0692 ; + A SPECIAL
0693 ; + C JMP TO INITIALIZATION
0694 ; + F NOT USED
0695 ;
0696 ;
0697 EDITRV = $E400 58368 EDITOR
0698 SCRENV = $E410 58384 SCREEN
0699 KEYBDV = $E420 58400 KEYBOARD
0700 PRINTV = $E430 58416 PRINTER
0701 CASETV = $E440 58432 CASSETTE
0702 ;
0703 ; ROM VECTORS
0704 ;
0705 DSKINV = $E453 58451
0706 CIOV = $E456 58454
0707 SIOV = $E459 58457
0708 SYSVBV = $E45F 58463
0709 VBIVAL = $E460 58464 ADR AT VVBLKI
0710 XITVBV = $E462 58466 EXIT VBI
0711 VBIXVL = $E463 58467 ADR AT VVBLKD
0712 BLKBDV = $E471 58481 MEMO PAD MODE
0713 WARMSV = $E474 58484
0714 COLDSV = $E477 58487
APPENDIX C
MEMORY USE
Page 0
$00-$7F
Operating system zero-page. The entire first half of page zero is
reserved for the operating system.
$80-$FF
Free zero-page. The top half of page zero is free if BASIC is
disabled. BASIC uses all but $CB-$D1. The floating point math
routines use $D4-$FF. If the floating point arithmetic package is not
used this memory is free.
Page 1
$100-1FF
This is the 6502 stack. The stack pointer initialized to $1FF and
moves downward as the stack is filled.
Pages 2-5
$200-$47F
This area is used for operating system database variables. Parts
which are not used in some particular programs, such as the cassette
buffer or printer buffer, may then be used for other purposes. See
the O.S. equate listing for these locations.
$480-$57D ($480-$6FF if no floating point)
This is called the user work space. It is free to be used by
programs. If the floating point arithmetic package is not used the
user work space extends to $6FF. This area is used by BASIC.
$57E-$5FF
This area is used by the floating point arithmetic package. It is
free if the package is not used.
Page 6
$600-6FF
Atari has solemnly sworn never to put anything in this page of
memory.
Page 7-the screen region
$700
This is called the boot region. Most machine language programs which
don't use DOS load at this address. DOS extends from $700-$1CFB.
MEMLO
The address pointed to by the O.S. database variable MEMLO [$02E7,2
(743)] is the first byte of free memory. This pointer is usually
changed by any program's initialization routine. For example, upon
power-up, MEMLO points to $700. When DOS loads in, DOS changes MEMLO
to point to $2A80. If an AUTORUN.SYS program then loads in just above
DOS, such as DISKIO, it will usually change MEMLO to point above
itself. One important reason for this is to protect the program from
BASIC. BASIC uses memory starting at MEMLO.
MEMTOP
MEMTOP [$2E5,2 (741)] is set by the O.S. whenever a graphics mode is
entered. The graphics region is at the very top of ram and extends
downward. The address MEMTOP points to depends on how much memory the
screen region uses.
APPMHI
APPMHI [$0E,2 (14)] should be set by any program to point to the
highest address required by the program. If the O.S. cannot set up a
screen without going below APPMHI it will return a
not-enough-memory-for-screen-mode error.
The cartridge slots
$8000 (32768)
This is the beginning of the 8K bytes used by the right cartridge slot
of the 800. This is also where 16K cartridges begin. If there is no
cartridge here it is ram.
$A000 (40960)
This is the beginning of the left cartridge of the 800 or the only
cartridge slot on all other models. This is where the BASIC ROM
resides in the XL/XE models. This area is RAM is there is no
cartridge or BASIC is disabled on XL/XE models.
above the cartridges
$C000-$CFFF (49152-53247)
This area is empty on the 800. Sometimes special ROM chips, such as
Omnimon are wired in here. On the XL/XE models $C000-C7FF is free ram
if there are no cartridges. On XL/XE models, the O.S. ROM starts at
$C800
$D000-$D7FF (53248-57373)
This area is taken up by the hardware chips. The chips actually take
only a fraction of this space. If these addresses are further decoded
there is space for many, many more hardware chips. For example, The
PIA chip uses 256 bytes of memory but needs only 4 bytes. There is
room for 64 PIA chips in this reserved memory.
$E000-E3FF (57344-58367)
This is the location of the ATASCII character set.
$E400-FFF7 (58368-65527)
This is the operating system ROM
$FFF8-$FFFF (65528-65535)
These last 8 bytes contain the addresses of the interrupt vectors.
Upon power up the 6502 gets a reset pulse and looks up the reset
routine here.
- 1 -
XMODEM/YMODEM PROTOCOL REFERENCE
A compendium of documents describing the
XMODEM and YMODEM
File Transfer Protocols
This document was formatted 9-11-86.
Edited by Chuck Forsberg
Please distribute as widely as possible.
Questions to Chuck Forsberg
Omen Technology Inc
17505-V Sauvie Island Road
Portland Oregon 97231
Voice: 503-621-3406
Modem (Telegodzilla): 503-621-3746 Speed 1200,300
Compuserve: 70007,2304
UUCP: ...!tektronix!reed!omen!caf
- 2 -
1. ROSETTA STONE
Here are some definitions which reflect the current vernacular
in the computer media. The attempt here is identify the file
transfer protocol rather than specific programs.
XMODEM refers to the original 1979 file transfer etiquette
introduced by Ward Christensen's 1979 MODEM2 program. It's also
called the MODEM or MODEM2 protocol. Some who are unaware of MODEM7's
unusual batch file mode call it MODEM7. Other aliases include "CP/M
Users's Group" and "TERM II FTP 3". This protocol is supported by
every serious communications program because of its universality,
simplicity, and reasonable performance.
XMODEM/CRC replaces XMODEM's 1 byte checksum with a two byte Cyclical
Redundancy Check (CRC-16), giving modern error detection
protection.
XMODEM-1k Refers to the XMODEM/CRC protocol with 1024 byte data blocks.
YMODEM refers to the XMODEM/CRC (optional 1k blocks) protocol with the
batch transmission described below.
ZMODEM uses familiar XMODEM/CRC and YMODEM technology in a
new protocol that provides reliability, throughput, file
management, and user amenities appropriate to contemporary
data communications.
2. YET ANOTHER PROTOCOL?
Since its development half a decade ago, the Ward Christensen modem
protocol has enabled a wide variety of computer systems to interchange
data. There is hardly a communications program that doesn't at least
claim to support this protocol.
Recent advances in computing, modems and networking have
revealed a number of weaknesses in the original protocol:
+ The short block length caused throughput to suffer when used with
timesharing systems, packet switched networks, satellite circuits,
and buffered (error correcting) modems.
+ The 8 bit arithmetic checksum and other aspects allowed line
impairments to interfere with dependable, accurate transfers.
+ Only one file could be sent per command. The file name had to be
given twice, first to the sending program and then again to the
receiving program.
+ The transmitted file could accumulate as many as 127 extraneous
bytes.
Chapter 2
X/YMODEM Protocol Reference 09-11-86 3
+ The modification date of the file was lost.
A number of other protocols have been developed over the
years, but none have displaced XMODEM to date:
+ Lack of public domain documentation and example programs have kept
proprietary protocols such as MNP, Blast, and others
tightly bound to the fortunes of their suppliers.
+ Complexity discourages the widespread application of BISYNC, SDLC,
HDLC, X.25, and X.PC protocols.
+ Performance compromises and moderate complexity have limited the
popularity of the Kermit protocol, which was developed to allow file
transfers in environments hostile to XMODEM.
The XMODEM protocol extensions and YMODEM Batch address these
weaknesses while maintaining XMODEM's simplicity.
YMODEM is supported by the public domain programs YAM (CP/M),
YAM(CP/M-86), YAM(CCPM-86), IMP (CP/M), KMD (CP/M), rz/sz (Unix, Xenix,
VMS, Berkeley Unix, Venix, Xenix, Coherent, IDRIS, Regulus). Commerical
implementations include MIRROR, and Professional-YAM.[1] Communications
programs supporting these extensions have been in use since 1981.
The 1k packet length (XMODEM-1k) described below may be used in
conjunction with YMODEM Batch Protocol, or with single file transfers
identical to the XMODEM/CRC protocol except for minimal
changes to support 1k packets.
Another extension is simply called the g option. It provides maximum
throughput when used with end to end error correcting media,
such as X.PC and error correcting modems, including the emerging
9600 bps units by Electronic Vaults and others.
To complete this tome, Ward Christensen's original protocol document and
John Byrns's CRC-16 document are included for reference.
References to the MODEM or MODEM7 protocol have been changed
to XMODEM to accommodate the vernacular. In Australia, it is
properly called the Christensen Protocol.
__________
1. Available for IBM PC,XT,AT, Unix and Xenix
Chapter 2
X/YMODEM Protocol Reference 09-11-86 4
2.1 Some Messages from the Pioneer
#: 130940 S0/Communications 25-Apr-85 18:38:47
Sb: my protocol
Fm: Ward Christensen 76703,302 (EDITED)
To: all
Be aware the article[2] DID quote me correctly in terms of the
phrases like "not robust", etc.
It was a quick hack I threw together, very unplanned (like
everything I do), to satisfy a personal need to communicate with
"some other" people.
ONLY the fact that it was done in 8/77, and that I put it in the public
domain immediately, made it become the standard that it is.
I think its time for me to
(1) document it; (people call me and say "my product is going
to include it - what can I 'reference'", or "I'm writing a
paper on it, what do I put in the bibliography") and
(2) propose an "incremental extension" to it, which might take
"exactly" the form of Chuck Forsberg's YAM protocol. He
wrote YAM in C for CP/M and put it in the public domain,
and wrote a batch protocol for Unix[3] called rb and sb
(receive batch, send batch), which was basically XMODEM with
(a) a record 0 containing filename date time and size
(b) a 1K block size option
(c) CRC-16.
He did some clever programming to detect false ACK or EOT, but basically
left them the same.
People who suggest I make SIGNIFICANT changes to the protocol,
such as "full duplex", "multiple outstanding blocks", "multiple
destinations", etc etc don't understand that the incredible
simplicity of the protocol is one of the reasons it survived to
this day in as many machines and programs as it may be found in!
Consider the PC-NET group back in '77 or so - documenting to
beat the band
- THEY had a protocol, but it was "extremely complex", because
it tried to be "all things to all people" - i.e. send binary
files on a 7-bit system, etc. I was not that "benevolent". I
(emphasize > I < ) had an 8-bit UART,
__________
2. Infoworld April 29 p. 16
3. VAX/VMS versions of these programs are also available.
Chapter 2
X/YMODEM Protocol Reference 09-11-86 5
so "my protocol was an 8-bit protocol", and I would just say "sorry" to
people who were held back by 7-bit limitations. ...
Block size: Chuck Forsberg created an extension of my protocol,
called YAM, which is also supported via his public domain
programs for UNIX called rb and sb - receive batch and send
batch. They cleverly send a "block 0" which contains the
filename, date, time, and size. Unfortunately, its UNIX style,
and is abit weird[4] - octal numbers, etc. BUT, it is a nice way
to overcome the kludgy "echo the chars of the name" introduced
with MODEM7. Further, chuck uses CRC-16 and optional 1K blocks.
Thus the record 0, 1K, and CRC, make it a "pretty slick new
protocol" which is not significantly different from my own.
Also, there is a catchy name - YMODEM. That means to some
that it is the "next thing after XMODEM", and to others that it
is the Y(am)MODEM protocol. I don't want to emphasize that too
much - out of fear that other mfgrs might think it is a
"competitive" protocol, rather than an "unaffiliated" protocol.
Chuck is currently selling a much-enhanced version of his
CP/M-80 C program YAM, calling it Professional Yam, and its
for the PC - I'm using it right now. VERY slick! 32K capture buffer,
script, scrolling, previously captured text search, plus
built-in commands for just about everything - directory (sorted
every which way), XMODEM, YMODEM, KERMIT, and ASCII file
upload/download, etc. You can program it to "behave" with most
any system - for example when trying a number for CIS it detects
the "busy" string back from the modem and substitutes a diff
phone # into the dialing string and branches back to try it.
3. XMODEM PROTOCOL ENHANCEMENTS
This chapter discusses the protocol extensions to Ward Christensen's
1982 XMODEM protocol description document.
The original document recommends the user be asked whether to continue
trying or abort after 10 retries. Most programs no longer ask the
operator whether he wishes to keep retrying. Virtually all correctable
errors are corrected within the first few retransmissions. If
the line is so bad that ten attempts are insufficient, there is
a significant danger of undetected errors. If the connection is
that bad, it's better to redial for a better connection, or
mail a floppy disk.
__________
4. The file length, time, and file mode are optional.The pathname and
file length may be sent alone if desired.
Chapter 3 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 6
3.1 Graceful Abort
The YAM and Professional-YAM X/YMODEM routines recognize a
sequence of two consecutive CAN (Hex 18) characters without modem
errors (overrun, framing, etc.) as a transfer abort command. This
sequence is recognized when YAM is waiting for the beginning of a
packet or for an acknowledge to one that has been sent. The
check for two consecutive CAN characters virtually eliminates the
possibility of a line hit aborting the transfer. YAM sends
eight CAN characters when it aborts an XMODEM, YMODEM, or ZMODEM
protocol file transfer. Pro-YAM then sends eight backspaces to delete
the CAN characters from the remote's keyboard input buffer, in
case the remote had already aborted the transfer and was
awaiting a keyboarded command.
3.2 CRC-16 Option
The XMODEM protocol uses an optional two character CRC-16
instead of the one character arithmetic checksum used by the original
protocol and by most commercial implementations. CRC-16
guarantees detection of all single and double bit errors, all errors
with an odd number of error bits, all burst errors of length 16 or
less, 99.9969% of all 17-bit error bursts, and 99.9984 per cent
of all possible longer error bursts. By contrast, a double bit
error, or a burst error of 9 bits or more can sneak past the
XMODEM protocol arithmetic checksum.
The XMODEM/CRC protocol is similar to the XMODEM protocol,
except that the receiver specifies CRC-16 by sending C (Hex
43) instead of NAK when requesting the FIRST packet. A two
byte CRC is sent in place of the one byte arithmetic checksum.
YAM's c option to the r command enables CRC-16 in single file
reception, corresponding to the original implementation in the
MODEM7 series programs. This remains the default because many
commercial communications programs and bulletin board systems still do
not support CRC-16, especially those written in Basic or Pascal.
XMODEM protocol with CRC is accurate provided both sender and
receiver both report a successful transmission. The protocol is robust
in the presence of characters lost by buffer overloading on
timesharing systems.
The single character ACK/NAK responses generated by the
receiving program adapt well to split speed modems, where the reverse
channel is limited to ten per cent or less of he main channel's speed.
XMODEM and YMODEM are half duplex protocols which do not attempt to
transmit information and control signals in both directions at the same
time. This avoids buffer overrun problems that have been reported by
users attempting to exploit full duplex asynchronous file transfer
protocols such as Blast.
Professional-YAM adds several proprietary logic enhancements to XMODEM's
Chapter 3 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 7
error detection and recovery. These compatible enhancements eliminate
most of the bad file transfers other programs make when using
the XMODEM protocol under less than ideal conditions.
3.3 XMODEM-1k 1024 Byte Packet
The choice to use 1024 byte packets is expressed to the sending
program on its command line or selection menu.[1] 1024 byte packets
improve throughput in many applications, but some environments cannot
accept 1024 byte bursts, especially minicomuters running 19.2kb
ports.
An STX (02) replaces the SOH (01) at the beginning of the transmitted
block to notify the receiver of the longer packet length. The
transmitted packet contains 1024 bytes of data. The receiver
should be able to accept any mixture of 128 and 1024 byte
packets. The packet number is incremented by one for each
packet regardless of the packet length.
The sender must not change between 128 and 1024 byte packet lengths if it
has not received a valid ACK for the current packet. Failure to observe
this restriction allows certain transmission errors to pass undetected.
If 1024 byte packets are being used, it is possible for a file to "grow"
up to the next multiple of 1024 bytes. This does not waste disk space if
the allocation granularity is 1k or greater. With YMODEM batch
transmission, the optional file length transmitted in the file
name packet allows the receiver to discard the padding,
preserving the exact file length and contents.
1024 byte packets may be used with batch file transmission or with single
file transmission. CRC-16 should be used with the k option to preserve
data integrity over phone lines. If a program wishes to enforce this
recommendation, it should cancel the transfer, then issue an informative
diagnostic message if the receiver requests checksum instead of CRC-16.
Under no circumstances may a sending program use CRC-16 unless the
receiver commands CRC-16.
4. YMODEM Batch File Transmission
The YMODEM Batch protocol is an extension to the XMODEM/CRC protocol that
allows 0 or more files to be transmitted with a single command. (Zero
files may be sent if none of the requested files is accessible.) The
design approach of the YMODEM Batch protocol is to use the
normal routines for sending and receiving XMODEM packets in a
layered fashion similar to
__________
1. See "KMD/IMP Exceptions to YMODEM" below.
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 8
Figure 1. 1024 byte Packets
SENDER RECEIVER
"s -k foo.bar"
"foo.bar open x.x minutes"
C
STX 01 FE Data[1024] CRC CRC
ACK
STX 02 FD Data[1024] CRC CRC
ACK
STX 03 FC Data[1000] CPMEOF[24] CRC CRC
ACK
EOT
ACK
Figure 2. Mixed 1024 and 128 byte Packets
SENDER RECEIVER
"s -k foo.bar"
"foo.bar open x.x minutes"
C
STX 01 FE Data[1024] CRC CRC
ACK
STX 02 FD Data[1024] CRC CRC
ACK
SOH 03 FC Data[128] CRC CRC
ACK
SOH 04 FB Data[100] CPMEOF[28] CRC CRC
ACK
EOT
ACK
packet switching methods.
Why was it necessary to design a new batch protocol when one already
existed in MODEM7?[1] The batch file mode used by MODEM7 is unsuitable
because it does not permit full pathnames, file length, file date, or
other attribute information to be transmitted. Such a restrictive design,
hastily implemented with only CP/M in mind, would not have permitted
extensions to current areas of personal computing such as Unix, DOS, and
object oriented systems. In addition, the MODEM7 batch file mode is
somewhat susceptible to transmission impairments.
__________
1. The MODEM7 batch protocol transmitted CP/M FCB bytes f1...f8 and
t1...t3 one character at a time. The receiver echoed these bytes as
received, one at a time.
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 9
As in the case of single a file transfer, the receiver initiates batch
file transmission by sending a "C" character (for CRC-16).
The sender opens the first file and sends packet number 0 with the
following information.[2]
Only the pathname (file name) part is required for batch transfers.
To maintain upwards compatibility, all unused bytes in packet 0 must be
set to null.
Pathname The pathname (conventionally, the file name) is sent as a null
terminated ASCII string. This is the filename format used by the
handle oriented MSDOS(TM) functions and C library fopen functions.
An assembly language example follows:
DB 'foo.bar',0
No spaces are included in the pathname. Normally only the file name
stem (no directory prefix) is transmitted unless the sender has
selected YAM's f option to send the full pathname. The source drive
(A:, B:, etc.) is never sent.
Filename Considerations:
+ File names should be translated to lower case unless the sending
system supports upper/lower case file names. This is a
convenience for users of systems (such as Unix) which store
filenames in upper and lower case.
+ The receiver should accommodate file names in lower and upper
case.
+ When transmitting files between different operating systems,
file names must be acceptable to both the sender and receiving
operating systems.
If directories are included, they are delimited by /; i.e.,
"subdir/foo" is acceptable, "subdir\foo" is not.
Length The file length and each of the succeeding fields are optional.[3]
The length field is stored in the packet as a decimal
string counting the number of data bytes in the file. The
file length does not include any CPMEOF (^Z) or other
garbage characters used to pad the last packet.
__________
2. Only the data part of the packet is described here.
3. Fields may not be skipped.
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 10
If the file being transmitted is growing during transmission, the
length field should be set to at least the final expected file
length, or not sent.
The receiver stores the specified number of characters, discarding
any padding added by the sender to fill up the last packet.
Modification Date The mod date is optional, and the filename and length
may be sent without requiring the mod date to be sent.
Iff the modification date is sent, a single space separates the
modification date from the file length.
The mod date is sent as an octal number giving the time the contents
of the file were last changed, measured in seconds from Jan 1 1970
Universal Coordinated Time (GMT). A date of 0 implies the
modification date is unknown and should be left as the date the file
is received.
This standard format was chosen to eliminate ambiguities
arising from transfers between different time zones.
Two Microsoft blunders complicate the use of modification dates in
file transfers with MSDOS(TM) systems. The first is the lack of
timezone standardization in MS-DOS. A file's creation time can not
be known unless the timezone of the system that wrote the file[4] is
known. Unix solved this problem (for planet Earth, anyway) by
stamping files with Universal Time (GMT). Microsoft would have to
include the timezone of origin in the directory entries, but does
not. Professional-YAM gets around this problem by using the z
parameter which is set to the number of minutes local time lags GMT.
For files known to originate from a different timezone, the -zT
option may be used to specify T as the timezone for an individual
file transfer.
The second problem is the lack of a separate file creation date in
DOS. Since some backup schemes used with DOS rely on the file
creation date to select files to be copied to the archive, back-
dating the file modification date could interfere with the safety of
the transferred files. For this reason, Pro-YAM does not modify the
date of received files with the header information unless the d
numeric parameter is non zero.
__________
4. Not necessarily that of the transmitting system!
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 11
Mode Iff the file mode is sent, a single space separates the file mode
from the modification date. The file mode is stored as an octal
string. Unless the file originated from a Unix system, the
file mode is set to 0. rb(1) checks the file mode for the
0x8000 bit which indicates a Unix type regular file. Files
with the 0x8000 bit set are assumed to have been sent from
another Unix (or similar) system which uses the same file
conventions. Such files are not translated in any way.
Serial Number Iff the serial number is sent, a single space separates the
serial number from the file mode. The serial number of the
transmitting program is stored as an octal string.
Programs which do not have a serial number should omit this
field, or set it to 0. The receiver's use of this field is
optional.
Other Fields YMODEM was designed to allow additional header fields to be
added as above without creating compatibility problems with older
YMODEM programs. Please contact Omen Technology if other fields are
needed for special application requirements.
The rest of the packet is set to nulls. This is essential to preserve
upward compatibility.[5]
If the filename packet is received with a CRC or other error, a
restrnsmission is requested. After the filename packet has been
received, it is ACK'ed if the write open is successful. If the
file cannot be opened for writing, the receiver cancels the
transfer with CAN characters as described above.
The receiver then initiates transfer of the file contents
according to the standard XMODEM/CRC protocol.
After the file contents have been transmitted, the receiver
again asks for the next pathname. Transmission of a null
pathname terminates batch file transmission. Note that
transmission of no files is not necessarily an error. This is
possible if none of the files requested of the sender could be
opened for reading.
In batch transmission, the receiver automatically requests CRC-16.
The Unix programs sz(1) and rz(1) included in the source code file
__________
5. If, perchance, this information extends beyond 128 bytes (possible
with Unix 4.2 BSD extended file names), the packet should be
sent as a 1k packet as described above.
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 12
RZSZ[12].SHQ (rzsz1.sh, rzsz2.sh) should answer other questions about
YMODEM batch protocol.
Figure 3. YMODEM Batch Transmission Session
SENDER RECEIVER
"sb foo.*"
"sending in batch mode etc."
C (command:rb)
SOH 00 FF foo.c NUL[123] CRC CRC
ACK
C
SOH 01 FE Data[128] CRC CRC
ACK
STX 02 FD Data[1024] CRC CRC
ACK
SOH 03 FC Data[128] CRC CRC
ACK
SOH 04 FB Data[100] CPMEOF[28] CRC CRC
ACK
EOT
NAK
EOT
ACK
C
SOH 00 FF NUL[128] CRC CRC
ACK
Figure 4. YMODEM Filename packet transmitted by sz
-rw-r--r-- 6347 Jun 17 1984 20:34 bbcsched.txt
00 0100FF62 62637363 6865642E 74787400 |...bbcsched.txt.|
10 36333437 20333331 34373432 35313320 |6347 3314742513 |
20 31303036 34340000 00000000 00000000 |100644..........|
30 00000000 00000000 00000000 00000000
80 000000CA 56
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 13
Figure 5. YMODEM Header Information used by various programs
_____________________________________________________________________
| Program | Batch | Length | Date | Mode | S/N | 1k-Blk | g-Option |
|___________|_______|________|______|______|_____|________|__________|
|Unix rz/sz | yes | yes | yes | yes | no | yes | sb only |
|___________|_______|________|______|______|_____|________|__________|
|VMS rb/sb | yes | yes | no | no | no | yes | no |
|___________|_______|________|______|______|_____|________|__________|
|Pro-YAM | yes | yes | yes | no | yes | yes | yes |
|___________|_______|________|______|______|_____|________|__________|
|CP/M YAM | yes | no | no | no | no | yes | no |
|___________|_______|________|______|______|_____|________|__________|
|KMD/IMP | yes | ? | no | no | no | yes | no |
|___________|_______|________|______|______|_____|________|__________|
4.1 KMD/IMP Exceptions to YMODEM
KMD and IMP character sequence emitted by the receiver (CK) to
automatically trigger the use of 1024 byte packets as an alternative to
specifying this option on this command line. Although this two character
sequence works well on single process micros in direct communication,
timesharing systems and packet switched networks can separate the
successive characters by several seconds, rendering this method
unreliable.
Sending programs may detect the CK sequence if the operating enviornment
does not preclude reliable implementation.
Receiving programs should retain the option of sending the
standard YMODEM C (not CK) trigger with the standard 10 second
timeout to insure compatibility with newer forms of
telecommunications technology.
5. YMODEM-g File Transmission
Developing technology is providing phone line data transmission at ever
higher speeds using very specialized techniques. These high
speed modems, as well as session protocols such as X.PC, provide
high speed, error free communications at the expense of
considerably increased delay time.
This delay time is moderate compared to human interactions, but it
cripples the throughput of most error correcting protocols.
The g option to YMODEM has proven effective under these circumstances.
The g option is driven by the receiver, which initiates the
batch transfer by transmitting a G instead of C. When the
sender recognizes the G, it bypasses the usual wait for an ACK
to each transmitted packet, sending succeeding packets at full
speed, subject to XOFF/XON or other flow control exerted by the medium.
Chapter 5 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 09-11-86 14
The sender expects an inital G to initiate the transmission of a
particular file, and also expects an ACK on the EOT sent at the end of
each file. This synchronization allows the receiver time to open and
close files as necessary.
If an error is detected in a YMODEM-g transfer, the receiver aborts the
transfer with the multiple CAN abort sequence. The ZMODEM protocol should
be used in applications that require both streaming throughput and error
recovery.
Figure 6. YMODEM-g Transmission Session
SENDER RECEIVER
"sb foo.*"
"sending in batch mode etc..."
G (command:rb -g)
SOH 00 FF foo.c NUL[123] CRC CRC
G
SOH 01 FE Data[128] CRC CRC
STX 02 FD Data[1024] CRC CRC
SOH 03 FC Data[128] CRC CRC
SOH 04 FB Data[100] CPMEOF[28] CRC CRC
EOT
ACK
G
SOH 00 FF NUL[128] CRC CRC
6. XMODEM PROTOCOL OVERVIEW
8/9/82 by Ward Christensen.
I will maintain a master copy of this. Please pass on changes or
suggestions via CBBS/Chicago at (312) 545-8086, CBBS/CPMUG (312) 849-1132
or by voice at (312) 849-6279.
6.1 Definitions
01H
04H
06H
15H
18H
43H
Chapter 6 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 15
6.2 Transmission Medium Level Protocol
Asynchronous, 8 data bits, no parity, one stop bit.
The protocol imposes no restrictions on the contents of the data being
transmitted. No control characters are looked for in the 128-byte data
messages. Absolutely any kind of data may be sent - binary, ASCII, etc.
The protocol has not formally been adopted to a 7-bit environment for the
transmission of ASCII-only (or unpacked-hex) data , although it could be
simply by having both ends agree to AND the protocol-dependent data with
7F hex before validating it. I specifically am referring to the
checksum, and the block numbers and their ones- complement.
Those wishing to maintain compatibility of the CP/M file structure, i.e.
to allow modemming ASCII files to or from CP/M systems should follow this
data format:
+ ASCII tabs used (09H); tabs set every 8.
+ Lines terminated by CR/LF (0DH 0AH)
+ End-of-file indicated by ^Z, 1AH. (one or more)
+ Data is variable length, i.e. should be considered a continuous
stream of data bytes, broken into 128-byte chunks purely for the
purpose of transmission.
+ A CP/M "peculiarity": If the data ends exactly on a 128-byte
boundary, i.e. CR in 127, and LF in 128, a subsequent sector
containing the ^Z EOF character(s) is optional, but is preferred.
Some utilities or user programs still do not handle EOF without ^Zs.
+ The last block sent is no different from others, i.e. there is no
"short block".
Figure 7. XMODEM Message Block Level Protocol
Each block of the transfer looks like:
<255-blk #><--128 data bytes-->
in which:
= 01 hex
= binary number, starts at 01 increments by 1, and
wraps 0FFH to 00H (not to 01)
<255-blk #> = blk # after going thru 8080 "CMA" instr, i.e.
each bit complemented in the 8-bit block number.
Formally, this is the "ones complement".
= the sum of the data bytes only. Toss any carry.
Chapter 6 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 16
6.3 File Level Protocol
6.3.1 Common_to_Both_Sender_and_Receiver
All errors are retried 10 times. For versions running with an operator
(i.e. NOT with XMODEM), a message is typed after 10 errors asking the
operator whether to "retry or quit".
Some versions of the protocol use , ASCII ^X, to cancel
transmission. This was never adopted as a standard, as having a
single "abort" character makes the transmission susceptible to
false termination due to an or being corrupted
into a and aborting transmission.
The protocol may be considered "receiver driven", that is, the
sender need not automatically re-transmit, although it does in
the current implementations.
6.3.2 Receive_Program_Considerations
The receiver has a 10-second timeout. It sends a every time it
times out. The receiver's first timeout, which sends a ,
signals the transmitter to start. Optionally, the receiver
could send a immediately, in case the sender was ready.
This would save the initial 10 second timeout. However, the
receiver MUST continue to timeout every 10 seconds in case the
sender wasn't ready.
Once into a receiving a block, the receiver goes into a
one-second timeout for each character and the checksum. If the
receiver wishes to a block for any reason (invalid header,
timeout receiving data), it must wait for the line to clear.
See "programming tips" for ideas.
Synchronizing: If a valid block number is received, it will be: 1) the
expected one, in which case everything is fine; or 2) a repeat of the
previously received block. This should be considered OK, and only
indicates that the receivers got glitched, and the sender re-
transmitted; 3) any other block number indicates a fatal loss of
synchronization, such as the rare case of the sender getting a
line-glitch that looked like an . Abort the transmission,
sending a
6.3.3 Sending_program_considerations
While waiting for transmission to begin, the sender has only a
single very long timeout, say one minute. In the current
protocol, the sender has a 10 second timeout before retrying. I
suggest NOT doing this, and letting the protocol be completely
receiver-driven. This will be compatible with existing programs.
When the sender has no more data, it sends an , and awaits an ,
resending the if it doesn't get one. Again, the protocol could be
receiver-driven, with the sender only having the high-level 1-minute
timeout to abort.
Chapter 6 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 17
Here is a sample of the data flow, sending a 3-block message.
It includes the two most common line hits - a garbaged block,
and an reply getting garbaged. represents the checksum byte.
Figure 8. Data flow including Error Recovery
SENDER RECEIVER
times out after 10 seconds,
<---
01 FE -data- --->
<---
02 FD -data- xx ---> (data gets line hit)
<---
02 FD -data- xx --->
<---
03 FC -data- xx --->
(ack gets garbaged) <---
03 FC -data- xx --->
--->
<---
--->
<---
(finished)
6.4 Programming Tips
+ The character-receive subroutine should be called with a parameter
specifying the number of seconds to wait. The receiver should first
call it with a time of 10, then and try again, 10 times.
After receiving the , the receiver should call the character
receive subroutine with a 1-second timeout, for the remainder of the
message and the . Since they are sent as a
continuous stream, timing out of this implies a serious
like glitch that caused, say, 127 characters to be seen
instead of 128.
+ When the receiver wishes to , it should call a "PURGE"
subroutine, to wait for the line to clear. Recall the sender tosses
any characters in its UART buffer immediately upon
completing sending a block, to ensure no glitches were mis-
interpreted.
The most common technique is for "PURGE" to call the character
receive subroutine, specifying a 1-second timeout,[1] and looping
back to PURGE until a timeout occurs. The is then sent,
ensuring the other end will see it.
__________
1. These times should be adjusted for use with timesharing systems.
Chapter 6 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 18
+ You may wish to add code recommended by John Mahr to your character
receive routine - to set an error flag if the UART shows framing
error, or overrun. This will help catch a few more glitches - the
most common of which is a hit in the high bits of the byte in two
consecutive bytes. The comes out OK since counting
in 1-byte produces the same result of adding 80H + 80H as
with adding 00H + 00H.
7. XMODEM/CRC Overview
1/13/85 by John Byrns -- CRC option.
Please pass on any reports of errors in this document or suggestions for
improvement to me via Ward's/CBBS at (312) 849-1132, or by voice at (312)
885-1105.
The CRC used in the Modem Protocol is an alternate form of block check
which provides more robust error detection than the original checksum.
Andrew S. Tanenbaum says in his book, Computer Networks, that the CRC-
CCITT used by the Modem Protocol will detect all single and double bit
errors, all errors with an odd number of bits, all burst errors of length
16 or less, 99.997% of 17-bit error bursts, and 99.998% of 18-bit and
longer bursts.
The changes to the Modem Protocol to replace the checksum with
the CRC are straight forward. If that were all that we did we
would not be able to communicate between a program using the old
checksum protocol and one using the new CRC protocol. An initial
handshake was added to solve this problem. The handshake allows
a receiving program with CRC capability to determine whether the
sending program supports the CRC option, and to switch it to CRC
mode if it does. This handshake is designed so that it will work
properly with programs which implement only the original
protocol. A description of this handshake is presented in section 10.
Figure 9. Message Block Level Protocol, CRC mode
Each block of the transfer in CRC mode looks like:
<255-blk #><--128 data bytes-->
in which:
= 01 hex
= binary number, starts at 01 increments by 1, and
wraps 0FFH to 00H (not to 01)
<255-blk #> = ones complement of blk #.
= byte containing the 8 hi order coefficients of the CRC.
= byte containing the 8 lo order coefficients of the CRC.
Chapter 7 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 19
7.1 CRC Calculation
7.1.1 Formal_Definition
To calculate the 16 bit CRC the message bits are considered to be the
coefficients of a polynomial. This message polynomial is first multiplied
by X^16 and then divided by the generator polynomial (X^16 + X^12 + X^5 +
1) using modulo two arithmetic. The remainder left after the division is
the desired CRC. Since a message block in the Modem Protocol is 128 bytes
or 1024 bits, the message polynomial will be of order X^1023.
The hi order bit of the first byte of the message block is the
coefficient of X^1023 in the message polynomial. The lo order
bit of the last byte of the message block is the coefficient of
X^0 in the message polynomial.
Figure 10. Example of CRC Calculation written in C
UPDCRC update routine from "rbsb.c". Refer to the source code for these
programs (contained in RZSZ1.SHQ and RZSZ2.SHQ) for usage. A fast table
driven macro is also included in this file.
/* update CRC */
unsigned short
updcrc(c, crc)
register c;
register unsigned crc;
{
register count;
for (count=8; --count>=0;) {
if (crc & 0x8000) {
crc <<= 1;
crc += (((c<<=1) & 0400) != 0);
crc ^= 0x1021;
else {
crc <<= 1;
crc += (((c<<=1) & 0400) != 0);
return crc;
7.2 CRC File Level Protocol Changes
7.2.1 Common_to_Both_Sender_and_Receiver
The only change to the File Level Protocol for the CRC option is the
initial handshake which is used to determine if both the sending and the
receiving programs support the CRC mode. All Modem Programs
should support the checksum mode for compatibility with older
versions. A receiving program that wishes to receive in CRC
mode implements the mode setting handshake by sending a in
place of the initial . If the sending program supports CRC
mode it will recognize the and will set itself into CRC
mode, and respond by sending the first block as if a had
been received. If the sending program does not support CRC mode it will
Chapter 7 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 20
not respond to the at all. After the receiver has sent the
it will wait up to 3 seconds for the that starts the
first block. If it receives a within 3 seconds it will
assume the sender supports CRC mode and will proceed with the
file exchange in CRC mode. If no is received within 3
seconds the receiver will switch to checksum mode, send a ,
and proceed in checksum mode. If the receiver wishes to use
checksum mode it should send an initial and the sending program
should respond to the as defined in the original Modem Protocol.
After the mode has been set by the initial or the protocol
follows the original Modem Protocol and is identical whether the checksum
or CRC is being used.
7.2.2 Receive_Program_Considerations
There are at least 4 things that can go wrong with the mode setting
handshake.
1. the initial can be garbled or lost.
2. the initial can be garbled.
3. the initial can be changed to a .
4. the initial from a receiver which wants to receive
in checksum can be changed to a .
The first problem can be solved if the receiver sends a second after
it times out the first time. This process can be repeated several times.
It must not be repeated too many times before sending a and
switching to checksum mode or a sending program without CRC support may
time out and abort. Repeating the will also fix the second problem if
the sending program cooperates by responding as if a were received
instead of ignoring the extra .
It is possible to fix problems 3 and 4 but probably not worth the trouble
since they will occur very infrequently. They could be fixed by switching
modes in either the sending or the receiving program after a large number
of successive s. This solution would risk other problems however.
7.2.3 Sending_Program_Considerations
The sending program should start in the checksum mode. This will insure
compatibility with checksum only receiving programs. Anytime a is
received before the first or the sending program should set
itself into CRC mode and respond as if a were received. The sender
should respond to additional s as if they were s until the first
is received. This will assist the receiving program in determining
the correct mode when the is lost or garbled. After the first
is received the sending program should ignore s.
Chapter 7 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 21
7.3 Data Flow Examples with CRC Option
Here is a data flow example for the case where the receiver requests
transmission in the CRC mode but the sender does not support the CRC
option. This example also includes various transmission errors.
represents the checksum byte.
Figure 11. Data Flow: Receiver has CRC Option, Sender Doesn't
SENDER RECEIVER
<---
times out after 3 seconds,
<---
times out after 3 seconds,
<---
times out after 3 seconds,
<---
times out after 3 seconds,
<---
01 FE -data- --->
<---
02 FD -data- ---> (data gets line hit)
<---
02 FD -data- --->
<---
03 FC -data- --->
(ack gets garbaged) <---
times out after 10 seconds,
<---
03 FC -data- --->
<---
--->
<---
Here is a data flow example for the case where the receiver requests
transmission in the CRC mode and the sender supports the CRC
option. This example also includes various transmission errors.
represents the 2 CRC bytes.
Chapter 7 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 22
Figure 12. Receiver and Sender Both have CRC Option
SENDER RECEIVER
<---
01 FE -data- --->
<---
02 FD -data- ---> (data gets line hit)
<---
02 FD -data- --->
<---
03 FC -data- --->
(ack gets garbaged) <---
times out after 10 seconds,
<---
03 FC -data- --->
<---
--->
<---
8. MORE INFORMATION
More information may be obtained by calling Telegodzilla at 503-621-3746.
Hit RETURNs for baud rate detection.Speed detection is automatic for 300,
1200, and 2400 bps.
A version this file with boldface, underlining, and superscripts for
printing on Epson or Gemini printers is available on Telegodzilla as
"YMODEME.DOC" or "YMODEME.DQC".
UUCP sites can obtain this file with
uucp omen!/usr/spool/uucppublic/ymodem.doc /tmp
A continually updated list of available files is stored in
/usr/spool/uucppublic/FILES.
The following L.sys line calls Telegodzilla (Pro-YAM in host operation).
Telegodzilla waits for carriage returns to determine the incoming speed.
If none is detected, 1200 bps is assumed and a greeting is displayed.
In response to "Name Please:" uucico gives the Pro-YAM "link"
command as a user name. The password (Giznoid) controls access
to the Xenix system connected to the IBM PC's other serial port.
Communications between Pro-YAM and Xenix use 9600 bps; YAM
converts this to the caller's speed.
Finally, the calling uucico logs in as uucp.
omen Any ACU 1200 1-503-621-3746 se:--se: link ord: Giznoid in:--in: uucp
Contact omen!caf if you wish the troff source files.
Chapter 8 Xmodem Protocol Overview
X/YMODEM Protocol Reference 09-11-86 23
9. Document Revisions
The September 11 1986 edition clarifies nomenclature and some minor
points. The April 15 1986 edition clarifies some points concerning CRC
calculations and spaces in the header.
10. YMODEM Programs
A demonstration version of Professional-YAM is available as ZMODEM.ARC
This may be used to test YMODEM amd ZMODEM implementations.
Unix programs supporting the YMODEM protocol are available on
Telegodzilla as RZSZ1.SHQ and RZSZ2.SHQ (SQueezed shell archives).
Most Unix like systems are supported, including V7, Xenix, Sys III,
4.2 BSD, SYS V, Idris, Coherent, and Regulus.
A version for VAX-VMS is available in VRBSB.SHQ.
Irv Hoff has added YMODEM 1k packets and basic YMODEM batch transfers to
the KMD and IMP series programs, which replace the XMODEM and
MODEM7/MDM7xx series respectively. Overlays are available for a wide
variety of CP/M systems.
Questions about YMODEM, the Professional-YAM communications program, and
requests for evaluation copies may be directed to:
Chuck Forsberg
Omen Technology Inc
17505-V Sauvie Island Road
Portland Oregon 97231
Voice: 503-621-3406
Modem: 503-621-3746 Speed: 2400,1200,300
Usenet: ...!tektronix!reed!omen!caf
Compuserve: 70007,2304
Source: TCE022
Chapter 10 Xmodem Protocol Overview
CONTENTS
1. ROSETTA STONE.................................................... 2
2. YET ANOTHER PROTOCOL?............................................ 2
2.1 Some Messages from the Pioneer.............................. 4
3. XMODEM PROTOCOL ENHANCEMENTS..................................... 5
3.1 Graceful Abort.............................................. 6
3.2 CRC-16 Option............................................... 6
3.3 XMODEM-1k 1024 Byte Packet.................................. 7
4. YMODEM Batch File Transmission................................... 7
4.1 KMD/IMP Exceptions to YMODEM................................ 13
5. YMODEM-g File Transmission....................................... 13
6. XMODEM PROTOCOL OVERVIEW......................................... 14
6.1 Definitions................................................. 14
6.2 Transmission Medium Level Protocol.......................... 15
6.3 File Level Protocol......................................... 16
6.4 Programming Tips............................................ 17
7. XMODEM/CRC Overview.............................................. 18
7.1 CRC Calculation............................................. 19
7.2 CRC File Level Protocol Changes............................. 19
7.3 Data Flow Examples with CRC Option.......................... 21
8. MORE INFORMATION................................................. 22
9. Document Revisions............................................... 23
10. YMODEM Programs.................................................. 23
- i -
LIST OF FIGURES
Figure 1. 1024 byte Packets......................................... 7
Figure 2. Mixed 1024 and 128 byte Packets........................... 7
Figure 3. YMODEM Batch Transmission Session......................... 12
Figure 4. YMODEM Filename packet transmitted by sz.................. 12
Figure 5. YMODEM Header Information used by various programs........ 13
Figure 6. YMODEM-g Transmission Session............................. 14
Figure 7. XMODEM Message Block Level Protocol....................... 15
Figure 8. Data flow including Error Recovery........................ 17
Figure 9. Message Block Level Protocol, CRC mode.................... 18
Figure 10. Example of CRC Calculation written in C................... 19
Figure 11. Data Flow: Receiver has CRC Option, Sender Doesn't........ 21
Figure 12. Receiver and Sender Both have CRC Option.................. 22
Last changes: 20 sep 1997
Feel free to contact me for any legal reason!
HeAvEn, Member of TaquarT