PRO-CT0

PRO-CT0 is an early gate array chip used as:
 * A sprite graphics multiplexer on AES carts and MVS boards, sometimes named ALPHA-8921, later replaced by and then.
 * 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 was the original chip name, from when Alpha Denshi used it on their Alpha68k system.

=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:

For specific details see Fatal Fury 2 and Super Sidekicks.

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