Just saw this project on GitLabs:
"Most read protected 16V8 and 20V8 can be read with this thing due to a bug in the read protection!"
"Every GAL has two trigger voltages on the EDIT-pin. One to switch into READ-mode and one to switch into WRITE-mode. Usually one can read the GAL putting 12V on the Edit pin. Putting 15-22V (depending on the GAL-Type) on the EDIT-pin triggers the writing mode."
"The read-protection can be fooled, if the read-voltage value is applied before power up (5V on VCC). Sometimes it needs to be close to the READ -trigger voltage (usually down to 9 V ~ 130 Potival) or around the WRITE-trigger voltage (PotiVal 220-230). Sometimes the read-protection is already fooled just by putting 12V (180 Potival) on EDIT before power up ."
"So try different values around 130, 180 and 220. A good read usually has a lot of zeros in each fuse line. Lines completely filled with "1" indicate an unsuccessfull read. Lines or blocks of lines complete filled with "0" are suspicious but could be possible. If you find a "sweet spot" but some lines are "1" try to read again. Sometimes a GAL need some "attempts" to be cracked."
Wonder if this would help decode the PLA chips on the Rejuvenator???