Sep 102019
 

As someone may recall I’ve recently done a reproduction of the custom ‘CUS99’ used on Namco PCBs :

Namco ‘CUS99’ reproduction

After done it I thought it was good to take into account its “companion” too, the ‘CUS98’  which most times come along with the first.Package is pretty the same but with two further pins than ‘CUS99’

 

But functions are totally different and,  as Rolling Thunder schematics suggest,  the main one is to generate the master reset :

Secondary functions are coin counters and lockouts handling as well as lamps driving, it seems only few games (like Pac-Land and Gaplus) use this last feature :

I was obviously interested in reproducing at least the reset generation function which is essential for correct operation of the PCB  (but it seems Rolling Thunder can boot into game also with a missing ‘CUS98’).Therefore, as usual, I studied earlier Namco hardware where the custom had not yet been used and I came to a prototype developed on a breadboard:

The protoytpe worked pretty good :

Hence I developed a proper board :

Final testing on a Pac-Land PCB:

As said some functions have been intentionally omitted favoring the needed ones (watchdog circuit ad reset switch were implemented too).This will at least allow to save PCBs with a faulty/broken or missing ‘CUS98’.

 Posted by at 8:10 am

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