SimonSoft's IDE-hardware for ATARI-computers.

Chapter 1, IDE-protocoll

Port / Addresses used in ATARI:
-------------------------------
 HEX.  DEC.  : read   : write
$D100 (54528): data   : data
$D101 (54529): error  : precomp (precomp is not used)
$D102 (54530): sector count     (sectors to r/w, 0=256 sectors)
$D103 (54531): sector number    (sector, 1 t/m max sec/cyl)
$D104 (54532): cylinder low     (0 t/m max)
$D105 (54533): cylinder high
$D106 (54534): Drive+Head       (master xxx0xxxx, slave xxx1xxxx)
$D107 (54535): Status : Command*

*)      Set                            :Cleared 
Bit 7 : busy                           :drive-logic is ready.
Bit 6 : ready for command              :busy or error.
Bit 3 : ready for data (after command) :error (invalid sector/head/cylinder).
Bit 1 : error during/after operation   :data transfer succesfull.

**)
Read this register to clear bit 1 or set bit 3 in status-register.

How to read/write :
-------------------
1) Read $D101 to clear any error-status.
2) Set requested drive+head (Master or Slave becomes now active)
3) Check if status bit7 is cleared and drive is ready for command.
4) Set requested sectornumber, cylinder and sector-count.
5) Write command in command-register.
READ)  command is $21
       wait for status bit3 to set
       Check for error (corrupt data)
       Read 512 bytes of data outof the data-register
WRITE) Command is $31
       Wait for status bit3 to set
       Write 512 bytes of data into the data-register
       Wait for status bit7 to clear (busy) and set (ready)
       Check for error (corrupt write)

(Edited 04-03-2000 By Mr. Atari. No warranty)