Atari System Reference manual


Written by Bob DuHamel (c)1987 
Hypertext version constructed by Ivo van Poorten (c)1994

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.


Table of contents
1. The Central Input/Output Utility (CIO)
2. The Disk Operating System (DOS)
3. Using the DOS 2 Utilities (DUP.SYS)
4. The Cassette Handler (C:)
5. The Keyboard Handler (K:)
6. The Printer Handler (P:)
7. The 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 Graphics
17. Sound
18. The Joystick Ports
19. Misc...
20. The XL and XE Models
A. Hardware Registers
B. Operating System Equates
C. Memory Use

Ivo van Poorten (ipoorten@cs.vu.nl)