ZN-2 Gameboard, anyone has a game board with PALs under chip 11?

[gorsonw]

I bought a non-working SFEX2+ Jamma board from eBay. At the back of chip socket #11, there are two surface mount PALs supposedly. I believe one of them was accidentally knocked off, so the game won't boot (CannotFindProgramCode I think the error was).

My other SFEX2+ board doesn't seem to have the same circuitry. Does anyone have a gameboard that is similar to this?

 

[Hammy]

This looks bootleg...

Can you show a better overall picture please?

 

[gorsonw]

What is also strange is, the game roms don't work on my other working EX2+ gameboard, same "CannotFindProgramCode" error. I also noticed on chip #5, one of the pins (i think D1 as per the datasheet) isn't connected like every other chip socket. If I bridge that pin to chip #6's D1, I get "System Error" which means the security chip (CP12) is not for the game (and vice versa).

The first game rom is marked "X2P 5" and I believe only the first chip is used to verify against the CP12. I suspect the missing PAL behind the board will bridge D1 conditionally if present.

 

[Hammy]

Very interesting! That is the newest PCB i've seen with the build code 99

Please dump the roms , this is a new version i think

RE; the missing chip = both should be possible to bypass with wire hacks but i don't have the schematic for this exact PCB.

 

[Blio Seri]

Aren't those chips there to obfuscate address or data lines? As a kind of "protection"...
If so that would explain why the ROMs doesn't work on your other board. But also gives you hope you can actually bypass them and use the "standard" ROMs.

[EDIT]
The S12HSC1A PAL is also used on Namco System 12 network PCB.

 

[Hammy]

Aren't those chips there to obfuscate address or data lines? As a kind of "protection"...

Could be, or just some obscure rom banking.

If so that would explain why the ROMs doesn't work on your other board.

Exactly, we need a dump to see what's going on...

The S12HSC1A PAL is also used on Namco System 12 network PCB.

This will be a n00b trying uselessly one from a scrap system 12, capcom would not use a part number like that.

 

[ekorz]

What evidence is there that the ‘missing’ chip was even populated to begin with? Couldn’t the fault just as easily be somewhere else? Mine doesn’t even have a mask rom in 11 anyway!

 

[Blio Seri]

This will be a n00b trying uselessly one from a scrap system 12, capcom would not use a part number like that.

You're probably right, soldering doesn't look factory.
Good point @ekorz

 

[gorsonw]

What evidence is there that the ‘missing’ chip was even populated to begin with? Couldn’t the fault just as easily be somewhere else? Mine doesn’t even have a mask rom in 11 anyway!

Yep, it could be possible that the fault is somewhere else but the fact that there is dead solder on the pads where the missing PAL is and chip #5's D1 leads to the missing PAL and one of the other pads of the missing PAL connects to other mask rom's D1 make me think that the PAL has to exist for the board to function correctly.

SFEX2+ has 6 x 8Mb mask roms populated (#5 to #10), #11 is not populated.

 

[gorsonw]

Could be, or just some obscure rom banking.

Most likely the case. The pads of the missing PAL connect to these pins.

• Chip #5 D1
• Other chip's D1
• A14, A20, A16, A21, A0, A1
• CLK
• VCC
• BANK03's pin 19
• /OE (as per the datasheet, I didn't trace where it leads to)
• GND

Exactly, we need a dump to see what's going on...

I don't have a ROM dumper, got a good and cheap one you can recommend? I could have built one myself but don't have the time.

This will be a n00b trying uselessly one from a scrap system 12, capcom would not use a part number like that.

There are apparently S12HSC1A, S12HSC2A and S12HSC3A according to https://github.com/MisterTea/MAMEHub/blob/master/Sources/Emulator/src/mame/drivers/namcos12.c.

The missing PAL could be a 2A or 3A?

I wonder what happens if I populate the missing PAL with the one right next to it.

 

[ekorz]

it’s not like you could swap on any other PAL, it’s whatever’s programmed on it that is important

 

[Hammy]

A14, A20, A16, A21, A0, A1

Sounds like address scramble!

I don't have a ROM dumper, got a good and cheap one you can recommend? I could have built one myself but don't have the time.

These are 64m mask so take a bit of work on most programmers , depends how much you are willing to spend depends how annoying the job will be!

I wonder what happens if I populate the missing PAL with the one right next to it.

Consider them both missing, those system 12 pld's are not correct.