PCM

NEO-PCM chip found in a MVS cartridge. Picture courtesy of [MVS-Scans].

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

File:Pcm pinout.png

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 A-1~V A22: V ROM(s) address bus