Seibu 'SEI80BU' reproduction

The 'SEI80BU'  (silkscreened on PCB as 'SEI0080BU' or simply '80') is a custom chip found on some Seibu Kaihatsu arcade PCBs like Toki, Cabal, Dynamite Duke, Raiden (encrypted version) and few others.

It comes in a SDIP42 package :

The chip is part of what is commonly referred as "Seibu Sound System" along with a Z80A, a YM3812, a YM3931 and an Oki MSM6295 or a MSM5205.

MAME emulates the 'SEI80BU' defining it as 'Encrypted Z80 Interface'.Anyway, the first thing to do when reproducing a chip is obtaining the pinout and, possibly, the direction of each pin.No other info were available so first of all I traced the connections of the chip on my PCBs and figured out it does more, acting as a clock divider too.Doing some prototyping on breadboard I was able to reproduce these functions quite easily.

Anyway, as said, the main role of the 'SEI80BU'  is to provide a decryption engine of Z80 sound CPU code (performing some data bits swap)

I don't have high programming skills (I'm mainly an hardware guy) so I asked my friend 'uchopon' (a skilled coder with a huge knowledge of arcade hardware) for some help.After few time he provided code of the encryption engine to be programmed in a complex programmable logic.I routed a board in which I implemented both the decryption engine (embedded in a small CPLD) and the clock dividing circuit.This was the result :

Usually CPLD based replacements need to be tweaked because of timing incompatibility with the hosting hardware but in this case I was really surprised the reproduction worked perfectly on first try!

Here's testing on my Cabal and Toki PCBs:

Another custom IC preserved.Thanks again to my friend 'uchopon' for his invaluable help!

Namco '00xx' reproduction

Here's another custom IC I recently reproduced.It's the Namco '00xx', the video RAM addresser (basically the same as Pacman's "284" VRAM Addresser) used on :

• Dig Dug
• Galaga
• Super Pac-Man

Original custom IC come in  DIP28 600 mil package with stamped number of four digits (but the 3rd and 4th digits can vary because they actually refers to the lot/date production hence the first two digits really matters) :

I made a TTL thru-hole prototype board :

It worked fine on first try.Here's successful testing on a Galaga PCB :

 

 

 

Next step will be a surface mounted TTL or CPLD based version, stay tuned!