Re: [stella] Megacart Specs

Subject: Re: [stella] Megacart Specs
From: bwmott@xxxxxxxxxxxx
Date: Mon, 13 Apr 1998 10:04:04 -0400 (EDT)
> At 09.26 12/04/98 -0400, bwmott@xxxxxxxxxxxx wrote:
> >It has some sort of pointer registers in it.  The idea is that you set
> >the register to point somewhere in the ROM then each time you read
> >from the register it automatically increments the pointer to the next
> >address.  This saves you from having to do that manually.  These pointer
> >registers also have bounds on them I believe.  When the pointer is outside
> >the bounds the data read is always zero.
> Do you know how this feature was used in Pitfall 2, besides the background
> soundtrack?

It's been a while since I looked at the Pitfall 2 code, but I seem
to recall that it used these registers for sound as well as graphics.
I'm almost positive that it was using them for loading the playfield
graphics and I believe it used them for player graphics as well.

It seems to me that these registers could be used for just about anything
sound, graphics, and colors.

Basically the game's kernel could consist of reading from these registers
and sticking the values in the correct TIA registers.  Then during
VBLANK you could setup the pointers for the next frame.  I guess for
complex games you might reset the pointers several times during a frame.


Bradford W. Mott (bwmott@xxxxxxx)          Computer Science Department           North Carolina State University

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