>This circuit was designed for a 32K ROM, though it should work on 8, 16, and
>32K ROMs. (I also assumed 8000-ffff was cart space. Correct me if I'm wrong
>on this (so I can fix the circuit and code example)
The cart space is $4000-$FFFF.
>start: lda #0000 1110b ;disable BIOS, enable sel 3, A12 on cart
> sta 03fh ;write to port
> lda #0000 1101b ;same as above plus "lockout" bit
> sta 03fh ;all stuff is enabled, latch disabled
> ldx #0ffh
Is $3f a special register for your circuit or are you trying to write
to the 7800 state control register? If it's the later, I think you are
aiming a bit too high. This register can only be accessed through addresses
$00-$1F. This is so that the 7800 can display the Atari logo while it
still tries to find out if a 2600 or a 7800 game is inserted, since the
MARIA graphics registers are above $20. Also I think you might have mixed
up the bits. The last value you are writing to the register will enable
the game ROM, but it also will disable the MARIA and the extra RAM.
The correct value for locking in a 7800 game with full MARIA and RAM
support should be %0000 0111.
> And the vectors will need to be located two places in the ROM-
> one with A12 and A14 both low. (AFFC, AFFD for the reset
> vector.)
But then the game ROM would have to be at least 32kb, right?
Thanks, Eckhard Stolberg
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