Template for Mattel Aquarius extension ROM (with header signature)

aq_romext.asm

; Basic template of a Mattel Aquarius extension ROM
;   build: z80asm -o aq_romext.bin aq_romext.asm
;   run: mame aquariusp -bp . -cart1 aq_romext.bin

; uncomment the following block to create a 16K ROM
;org 0xc000
; ...
; ### lower part of a 16K ROM ###
; ...
;	ds 0xe000 - $

; ### Header ###

; can be customized
H0: equ 0
H1: equ 0
H2: equ 0
H3: equ 0
H4: equ 0
H6: equ 0
H8: equ 0
HA: equ 0
HC: equ 0

; signature: fixed values
H5: equ 0x9c
H7: equ 0xb0
H9: equ 0x6c
HB: equ 0x64
HD: equ 0xA8
HF: equ 0x70


HE: equ (HF - 0x4e - (H3 + H4 + H5 + H6 + H7 + H8 + H9 + HA + HB + HC + HD)) & 0xff

if H3 == 0xf7
error
endif

org 0xe000
; ROM signature
	db H0
	db H1
	db H2
	db H3
	db H4
	db H5
	db H6
	db H7
	db H8
	db H9
	db HA
	db HB
	db HC
	db HD
	db HE
	db HF

; ### high part of the ROM ###

PRNCHR: equ 0x1d94

start:
	ld	a,'@'
	call    PRNCHR

hang:
	jp hang

	ds 0x10000 - $	; pad to the ROM size

Hi @bushy555, briefly looking at your work to port to Aquarius, I could notice a few things:

• in order to be accepted by mame, ROM files have to be exactly 8K or 16K
• some engines (at least juston) rely on modifying the code (inject delay values or addresses). This is not possible when the code executes from ROM. 2K of RAM are available at 0x3800 if you need to store values.

Thanks. Makes so much more sense.