45-in-1 (JY-120A) Multicart (Mapper 90)-how it switches CHR?
Posted: Mon May 08, 2017 9:46 am
I am trying to deduce how this multicart game switches CHR-BANKS (it's mapper 90, 128 PRG-BANKS, 256 CHR-BANKS). I created breakpoints:
but none of them is executed for games like:
8. ninja 2
9. ninja 3
10. bb cart
and so on
Looking at the pattern tables in FCEUX, it is clear that after choosing any of those games, the pattern table set is changed..
Code: Select all
* cpu write at $9000-9007: CHR Regs (low bits)
* cpu write at $A000-A007: CHR Regs (high bits)
* cpu write at $D003: [M.BH HHHH]
M = Mirror CHR (very strange, see below)
B = CHR Block mode (0=enabled, 1=disabled)
H = CHR Block (when in block mode) <- this could change banks
* ppu write at $0000-$1fff
8. ninja 2
9. ninja 3
10. bb cart
and so on
Looking at the pattern tables in FCEUX, it is clear that after choosing any of those games, the pattern table set is changed..