PCM: Difference between revisions
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[[NEO-PCM2]] can also be found in late cartridges and with [[NEO-YSA2]]. | [[NEO-PCM2]] can also be found in late cartridges and with [[NEO-YSA2]]. | ||
On some [[cartridge | On some [[:Category:cartridge boards|Cartridge boards]], V A20~V A22 can be used to select which of the 4 possible V ROMs to use (decoded by a LS139). | ||
=Internal logic= | =Internal logic= | ||
Revision as of 09:21, 7 January 2013
V ROM banking and multiplexing chip, found in AES and MVS cartridges, and on ROM-only arcade boards. Used to multiplex V ROM (ADPCM-A and ADPCM-B) access to mixed-content ROM chips.
NEO-PCM2 can also be found in late cartridges and with NEO-YSA2.
On some Cartridge boards, V A20~V A22 can be used to select which of the 4 possible V ROMs to use (decoded by a LS139).
Internal logic
Takes advantage of the asynchronous reading from the YM2610. See YM2610 bus timing.
Verilog: todo.
Pinout
OpenOffice Draw file: File:Pcm.odg
Has an inverting gate on pins 26 and 27.
- SDPOE, SDROE, SDPMPX, SDRMPX: from the YM2610
- SDRAD0~SDRAD7: ADPCM-A multiplexed bus part
- SDPAD0~SDPAD7: ADPCM-B multiplexed bus part
- SDRA8,SDRA9,SDRA20~SDRA23: ADPCM-A address bus
- SDPA8~SDPA11: ADPCM-B address bus
- V D0~V D7: V ROM(s) data bus
- V A0~V A22: V ROM(s) address bus