PRO-CT0

PRO-CT0 is an early SDIP64 gate array chip used as:
 * A sprite graphics multiplexer on AES carts and MVS boards, sometimes named ALPHA-8921, later replaced by NEO-ZMC2 and then NEO-CMC.
 * Security device in Super Sidekicks and Fatal Fury 2 AES and MVS cartridges, also named SNK-9201.

The device probably wasn't intended to be used as as security measure at first.

ALPHA-8921 is the original chip name when Alpha Denshi designed it.

=Pinouts=

=Internal logic=

Kyuusaku's Verilog definition:

furrtek's version:



=Use as graphics multiplexer=



See NEO-ZMC2.

=Use as security device=



Used on PROG-G2 boards. It is found in Fatal Fury 2 and Super Sidekicks only. It was SNK's first attempt at protecting NeoGeo games.

The chip is tied to the 68k address and data bus, listens to word writes and replies on odd addresses in the $200000-$2FFFFF address range.

The game program expects the chip to reply with specific data depending on the values written to it and will freeze if they are wrong.

Address bus mapping:

Data bus mapping:



Emulation
MAME's HLE emulation (fatfury2_protection): []

Reads:
 * To $255550, $2FFFF0, $200000, $2FF000, $236000, $236008: return dataout >> 24;
 * To $236004, $23600C: return dataout >> 24 nibble swapped

Writes:
 * To $211112, with data = $1111: dataout = $FF000000
 * To $233332, with data = $3333: dataout = $0000FFFF;
 * To $244442, with data = $4444: dataout = $00FF0000;
 * To $255552, with data = $5555, read back from $255551, $2FFFF1, $200001, $2FF001: dataout = $FF00FF00
 * To $256782, with data = $1234, read back from $36000 or $36004: dataout = $F05A3601
 * To $242812, with data = $1824, read back from $36008 or $3600C: dataout = $81422418
 * To $255551, $2FFFF1, $2FF001, $236001, $236005, $236009, $23600D, with data = $20: shift dataout left one byte