> While I am waiting on a working video pcb, I was thinking replacing that Altera chip
> could theoretically fix that bus error. However, that chip being a EPM7064 LC84-15 is
> actually a CPLD meaning some additional programming/burning would need to be
> done...that is unless something else on one of these System Super 22 boards does the
> programming itself.
Looking at the EPM7064 datasheet, this is a preprogrammed EEPROM based CPLD. Therefore it would likely have been programmed at the factory, either before soldering, or more likely via a JTAG or debug port on the board.
> What does that Namco C407 chip actually consist of and the differences between the
> C407 and Altera EPM7064.
Very likely, Namco started out with a CPLD and as production volumes increased, they had a semi-custom (likely standard-cell) gate array manufactured. There might be some differences which may reflect in design changes between PCB revs.
Additionally it is likely that Namco was pushing the CPLD too hard (a lot of logic, high frequencies), which causes it to overheat and eventually fail.
> Are both an MCU that stores some video related info?
These are gate arrays that contain gate and register logic, not MCUs. A 1250-macrocell CPLD is too small to contain a soft CPU core. They likely do some sort of video processing, based on their function.
> Is any additional programming required before replacing that chip? Any contents to
> dump from either?
A new/blank/reclaimed EPM7064 would have to be programmed before use.
Meanwhile, a replacement C407 would already have the logic either produced at the factory, most likely being a standard cell gate array.
If you can fine an EPM7064LC44-7 or -10,
In order to dump one of these, one should first attempt to do so over JTAG (if the port can be identified on the board) or by desoldering and attempting to dump with a programmer that supports it. However, it is very likely that the security bit is set, which would require decap to attempt to remove protection.
> Does either chip have contents burned from a program rom?
Not sure what you're asking here. The EPM7064 would likely have been programmed over JTAG using a debug/programming fixture.
> Yes I am aware that chip is surface mounted meaning replacing will take a lot more
> skill hence why I'm saving this application for later hopefully once this feature is
> understood.
Yes. That is one reason JTAG-based in circuit programming is usually used for this.
EDIT: Looking more closely, if this is an EPM7064 and not an EPM7064S, there is no JTAG and it has to be programmed out of circuit. 
The EPM7064S is a much better chip, but the format of the bitstream (the "code" that defines the register and gate logic on it) is almost certainly different and therefore incompatible... and reverse-engineering PLD bitstreams is not particularly fun.
Edited by balrog (01/08/19 03:25 AM)
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