> >One more question: the location of the register that controls the
> >playfield color: is that located on zero page, or where?
Yes, all TIA registers are zero page.(Unless I missed something) I
believe they are mirrored elsewhere in the memory map as well.
> When it comes to RAM, the 2600 only has 128 bytes which are part of the
> RIOT chip, and don't all 128 of them map to the 6507s zero page?
>From what I read, the PIA's address space is mapped into both the zero and
the one page. Hence the ram at $80-$FF is mirrored at $0180 and $01FF.
Programs typically put variables in the zero page mirror of the ram,
whereas the stack is access in the one page mirror. The stack must be on
the one page, the programmer has no control over that. This is defined in
the 6507 hardware. The stack pointer is only an 8 bit data register,
while the address bus is 13 bits(logically 16). When a stack operation
occurs, the processor uses $01 as the upper bits.
Does anyone have a comprehensive memory map for the VCS? (including all
the mirrors of various parts?) It would be really helpful, especially
when doing in-cart hardware.
Mark
--
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
