PLA replacement module for C64

Design by: 7073

This is a replacement module for the PLA chip found in the Commodore 64 computer. It uses a CPLD chip rather than a EEPROM chip. A CPLD is way much faster than EEPROM and more versatile. Provision has been made for using either a XC9536 CPLD (5V) or XC9536XL (3.3V, 5V tolerant). Besides the CPLD, the board needs a 100nF 0805 ceramic capacitor, and in case the XL version is to be used, a 3.3V LDO regulator (LM1117-3.3, SOT-223 case) and two more capacitors are needed. For XC9536, don't add the LDO regulator. Instead, use a solder blob to join the input and output pins so the CPLD receives 5V straight from the main board. Place a 100nF 0805 capacitor on either C1, C2 or C3. For ZX9536XL, add all the LDO regulator and the three capacitors. C1 is 100nF, C2 and C3 are 10uF. All capacitors are 0805. Source code and JED for both CPLD versions is at the provided link. ATM, board tested with XC9536 with success in a previously dead C64 board. XC9536XL version not yet tested in the wild.