Namco Pac-Man/Custom IC Pinouts: Difference between revisions
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== Pinouts == | == Pinouts == | ||
=== NVC285 - Z80 Sync Bus Controller === | === NVC285 - Z80 Sync Bus Controller === | ||
The NVC285 controls the passage of data between the Z80's CPU data bus (D0-D7) and the buffered data bus (DB0-DB7) | The NVC285 controls the passage of data between the Z80's CPU data bus (D0-D7) and the buffered data bus (DB0-DB7), synchronizes the CPU with RAM and internally holds a value used for the interrupt vector. | ||
.---\/---. | .---\/---. | ||
6M* -> |01 28| -- VCC | 6M* -> |01 28| -- VCC | ||
| Line 44: | Line 43: | ||
== Discrete logic replacements == | == Discrete logic replacements == | ||
Likely due to the success of Pac-Man in the states, Fujitsu couldn't keep up with the demand for these custom ICs. Therefore small circuit boards with discrete 74-series logic replicating their functionality were often used as replacements. These replacements are common on Midway Pac-Man boards. This also made it easier for bootleg copies of Pac-Man boards to be distributed. | Likely due to the success of Pac-Man in the states, Fujitsu couldn't keep up with the demand for these custom ICs. Therefore small circuit boards with discrete 74-series logic replicating their functionality were often used as replacements. These replacements are common on Midway Pac-Man boards. This also made it easier for bootleg copies of Pac-Man boards to be distributed. | ||
<!--to do: write signal descriptions and recreate schematics of these replacement pcbs--> | <!--to do: write signal descriptions and recreate schematics of these replacement pcbs--> | ||
Latest revision as of 07:59, 25 May 2023
The Namco Pac-Man logic board features a pair of custom integrated circuits manufactured by Fujitsu for Namco, perhaps intended to deter reverse-engineering and prevent piracy of the logic board. However, this didn't prevent bootlegging of the hardware by other companies.
Pinouts
NVC285 - Z80 Sync Bus Controller
The NVC285 controls the passage of data between the Z80's CPU data bus (D0-D7) and the buffered data bus (DB0-DB7), synchronizes the CPU with RAM and internally holds a value used for the interrupt vector.
.---\/---.
6M* -> |01 28| -- VCC
1H -> |02 27| <- /CS
2H -> |03 26| <- /M1
DB4 <> |04 25| <> D4
DB3 <> |05 24| <> D3
DB5 <> |06 23| <> D5
DB6 <> |07 22| <> D6
DB2 <> |08 21| <> D2
DB7 <> |09 20| <> D7
DB0 <> |10 19| <> D0
DB1 <> |11 18| <> D1
CK <- |12 17| <- /WREQ
R/W <- |13 16| <- /RD
GND -- |14 15| <- /IORQ
`--------'
NVC284 - VRAM Addresser
The NVC284 controls how the Tilemap and Color values in Video RAM are addressed to display the playfield. It is used to synchronize the Video and Work RAM with system timing, and to flip the playfield when in the game is in cocktail table mode.
.---\/---.
2H -> |01 28| -- VCC
4H -> |02 27| <- FLIP
8H -> |03 26| -> AB0
16H -> |04 25| -> AB1
32H -> |05 24| -> AB2
64H -> |06 23| -> AB3
128H -> |07 22| -> AB4
/256H -> |08 21| -> AB5
8V -> |09 20| -> AB6
16V -> |10 19| -> AB7
32V -> |11 18| -> AB8
64V -> |12 17| -> AB9
128V -> |13 16| -> AB10
GND -- |14 15| -> AB11
`--------'
Discrete logic replacements
Likely due to the success of Pac-Man in the states, Fujitsu couldn't keep up with the demand for these custom ICs. Therefore small circuit boards with discrete 74-series logic replicating their functionality were often used as replacements. These replacements are common on Midway Pac-Man boards. This also made it easier for bootleg copies of Pac-Man boards to be distributed.
