Z80 port map: Difference between revisions
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Some infos from [[User:kyuusaku]] | |||
The decode mask for '''reading''' ports is always $0C. The one for writes is indicated for each case. | |||
{| class="regdef" | {| class="regdef" | ||
|''' | |'''Address''' | ||
|'''Read''' | |'''Read''' | ||
|'''Write''' | |'''Write''' | ||
|'''[[Memory_mapped_registers#Address_decode_masks|Decode mask]]''' | |||
|- | |- | ||
|$00 | |$00 | ||
|Read sound code from 68k | | | ||
|Clear sound code from 68k to | *Read sound code from {{Chipname|68k}} | ||
*Acknowledge [[Z80 interrupts|NMI]] | |||
|Clear sound code from 68k to $00 | |||
|rowspan="2"|$0C | |||
|- | |- | ||
|$04 | |$04 | ||
|colspan="2"|[[YM2610]] I/O | |colspan="2"|[[YM2610]] I/O | ||
|- | |- | ||
|$08 | |$08 | ||
|Set [[Z80 memory map|$F000~$F7FF]] bank | |Set [[Z80 memory map|$F000~$F7FF]] bank | ||
|Enable | |rowspan="4"|Enable NMIs | ||
|rowspan="4"|$1C | |||
|- | |- | ||
|$09 | |$09 | ||
|Set $E000~$EFFF bank | |Set $E000~$EFFF bank | ||
|- | |- | ||
|$0A | |$0A | ||
|Set $C000~$DFFF bank | |Set $C000~$DFFF bank | ||
|- | |- | ||
|$0B | |$0B | ||
|Set $8000~$BFFF bank | |Set $8000~$BFFF bank | ||
|- | |- | ||
|$0C | |$0C | ||
| | |See {{Sig|SDRD1|SDRD1}} | ||
|[[68k/Z80_communication|Reply]] to 68k | |[[68k/Z80_communication|Reply]] to 68k | ||
|$0C | |||
|- | |- | ||
|$18 | |$18 | ||
| | |See address $08 | ||
|Disable | |Disable NMIs | ||
|$1C | |||
|} | |} | ||
Note that the [[M1 ROM|Z80 ROM]] bank selection is done 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. | 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). | The banks can then be chosen by putting the bank number in B, the port number in C and doing IN A,(C). | ||
This is handled by {{Chipname|NEO-ZMC}} in cartridges. | |||
[[Category:Base system]] | [[Category:Base system]] | ||
Revision as of 00:36, 12 October 2016
Some infos from User:kyuusaku
The decode mask for reading ports is always $0C. The one for writes is indicated for each case.
| Address | Read | Write | Decode mask |
| $00 | Clear sound code from 68k to $00 | $0C | |
| $04 | YM2610 I/O | ||
| $08 | Set $F000~$F7FF bank | Enable NMIs | $1C |
| $09 | Set $E000~$EFFF bank | ||
| $0A | Set $C000~$DFFF bank | ||
| $0B | Set $8000~$BFFF bank | ||
| $0C | See SDRD1 | Reply to 68k | $0C |
| $18 | See address $08 | Disable NMIs | $1C |
Note that the Z80 ROM bank selection is done 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). This is handled by NEO-ZMC in cartridges.