Difference between revisions of "A78 Header Specification"
From 8BitDev.org - Atari 7800 Development Wiki
(Created page with "==History and Purpose== The A78 header was originally created by Dan Boris, in tandem with his A7800 emulator. The header, which is added to the beginning of ROM images, serv...") |
(No difference)
|
Revision as of 17:05, 6 November 2015
History and Purpose
The A78 header was originally created by Dan Boris, in tandem with his A7800 emulator. The header, which is added to the beginning of ROM images, serves to tell the emulator which hardware should be present for the game to run correctly.
The format has ben expanded to incorporate new hardware, and is now being used by several emulators and the Concerto 7800 flash cart.
A78 Header in DASM format
To add an A78 header to your DASM source code, you can add or include the header at the start of your source, and adjust the fields to encode the hardware your game requires.
SEG ROM
HEADER ORG ROMTOP-128
DC.B 1 ; 0 Header version - 1 byte
DC.B "ATARI7800" ; 1..16 "ATARI7800 " - 16 bytes
DS 7,32
DC.B "Your Name Here"; 17..48 Cart title - 32 bytes
DS HEADER+49-.,0
DC.B $00,$00,256->ROMTOP,$00; 49..52 data length - 4 bytes
DC.B $00,$00 ; 53..54 cart type - 2 bytes
; bit 0 - pokey at $4000
; bit 1 - supergame bank switched
; bit 2 - supergame ram at $4000
; bit 3 - rom at $4000
; bit 4 - bank 6 at $4000
; bit 5 - supergame banked ram
; bit 6 - pokey at $450
; bit 8-15 - Special
; 0 = Normal cart
DC.B 1 ; 55 controller 1 type - 1 byte
DC.B 1 ; 56 controller 2 type - 1 byte
; 0 = None
; 1 = Joystick
; 2 = Light Gun
DC.B 0 ; 57 0 = NTSC 1 = PAL
DC.B 0 ; 58 Save data peripheral - 1 byte (version 2)
; 0 = None / unknown (default)
; 1 = High Score Cart (HSC)
; 2 = SaveKey
ORG HEADER+63
DC.B 0 ; 63 Expansion module
; 0 = No expansion module (default on all currently released games)
; 1 = Expansion module required
ORG HEADER+100 ; 100..127 "ACTUAL CART DATA STARTS HERE" - 28 bytes
DC.B "ACTUAL CART DATA STARTS HERE"
ROMTOP ORG $8000
