Z80 port map: Difference between revisions
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|Disable NMI | |Disable NMI | ||
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Revision as of 16:55, 18 December 2013
| Number | Read | Write |
| $00 | Read sound code from 68k | Clear sound code buffer |
| $04~$07 | YM2610 I/O | |
| $08 | Set $F000~$F7FF bank | Enable NMI |
| $09 | Set $E000~$EFFF bank | |
| $0A | Set $C000~$DFFF bank | |
| $0B | Set $8000~$BFFF bank | |
| $0C | Reply to 68k | |
| $18 | Disable NMI | |
Bank selection is made by reading ports. SNK used an obscure feature of the Z80: when accessing ports, the entire address bus is set, not only the lower 8 bits.
The banks can then be chosen by putting the bank number in B, the port number in C and doing IN A,(C). Or by putting the bank number in A and doing IN A,(Port). (to verify)