Can a GQ-4x4 ROM Programmer read and write to Programmable Logic Array's (PLA's)?

[alejack12001]

I am rebuilding a second AT&T 6300. I have discovered that the motherboard of this machine was showing parity error's in BANK 0. The RAM in that BANK is 4164-15, which are soldered to the motherboard. As yet, I have only engaged the AT&T system test disk to discover the parity error; but have not discovered which chip(s) are causing the error. I know I can use CheckIt to try to discover the faulty chip. The bottom line here is that if one or more chips are exhibiting a parity error they would have to be removed from the motherboard by desoldering them.

Not relishing the idea of desoldering the chips; I searched and found a second motherboard that I believe I purchased years ago from a computer show. The board was stripped of the CPU, serial, keyboard, timer, EPROMS, removable RAM, and PLA's. Most of the other missing chips I had as I usually keep at least two spares to serve me, should one fail.

I have the GQ-4x4 PROM programmer and UV eraser. I wanted to find out from the forum if the existing PLA's residing on the motherboard mentioned above can be read by the GQ and written to my secondary stock of PLA's?

 

[Chartreuse]

Most commercially used PLA/PAL/GAL chips are read locked so you would not be able to get the contents back. It's possible to reverse engineer one with some effort of locating the input and output pins and testing all possible combinations and such to work out the internal logic.

Looking at the supported devices list for the GQ-4x4, the only supported programmable logic devices listed are a number of CPLDs. Not the smaller GAL chips (like ATF22v10/GAL22v10 or GAL16v8) that are likely present on your 6300. I know the cheap TL866II programmer is capable of reading and writing these GAL devices (GAL is the more modern version of PAL logic chips and a drop in replacement).

 

[Chuck(G)]

Olivetti blew the security fuses on their PALs in the M24; see my blog for sussing out the equations for just one of them on the display board.

 

[alejack12001]

I looked over your programming effort for the PLA/PAL/GAL type chips. It's an impressive effort. My question is rather superficial; what did you use to implement the code to binary into the chips without blowing the fuse? I guess I'll have to transfer the PLA's from my existing board to the backup board; I only have the PROM reader/writer and since this doesn't work; what does work?