Toaplan "TWIN-CAM"

Toaplan, Raizing, original

A PAL or GAL16V8B that is responsible for generating timing signals for the discrete hardware text plane. Without it, there will be no image. It can also cause memory access issues with the text VRAM.

It can be bypassed at the expense of the text layer by removing the chip, and putting in a jumper between pin 1 and pin 12, which will cause the board to latch the graphics data from the GP9001 custom.

The name "TWIN-CAM" comes from the name printed on the chip in some middle-aged iterations. The name likely alludes to capturing data from two image sources.

Early chips are on PALCE16v8 devices and are unlocked. Later ones are on GAL16V8 devices and are locked. The first GAL16V8 devices have TWIN-CAM printed on them, while later ones do not.

The GAL is registered, soldered to the board, and locked, so it can not be trivially dumped. A replacement has been developed and tested in-circuit.

Pins 13-19 are outputs, while pins 1-9, and 12 are inputs. 11 is /OE and is tied to ground, so it may be ignored. Pin 3 is an inverted clock division fed back into the chip for unknown purposes.

Known Vendors🔗

Games Using This Part🔗

Hardware Using This Part🔗

Images and Diagrams🔗

TWIN-CAM on a Mahou Daisakusen PCB

TWIN-CAM on a Battle Garegga PCB

The bypass hack, done as a test

Repair Manuals🔗

No manuals currently added.

Repair Tips🔗

Bypass hotfix 🔗

The GAL can be bypassed at the expense of the text layer by removing the chip, and putting in a jumper between pin 1 and pin 12, which will cause the board to latch the graphics data from the GP9001 custom. This is a suitable workaround to verify that the board otherwise works.

Failure symptoms 🔗

If the game runs, but has a black screen, it is a good sign that U33 may be dead.

If the game won't boot past the initial self test, and/or fails on the Text RAM test, it could be an indication that one or more outputs from this chip has failed. Some outputs control address bus mastery for the text RAM - the CPU must master it when writing to the text RAM, but the readout must master it during active display.

GAL16V8 replacement 🔗

A replacement set of equations and compiled JED files are available to allow replacement of U33.

JED file (to burn to a GAL16V8): https://github.com/Mikejmoffitt/bgaregga-gals/raw/master/jed/BG_U33.JED

EQN source file: https://github.com/Mikejmoffitt/bgaregga-gals/blob/master/eqn/BG_U33.EQN