Commodore 64 PLA replacement
Commodore 64 PLA replacement
This project is an SMD version of the awesome Commodore 64 PLA -replacement by Daniel Mantione. Published under permission from Daniel.
This version uses 2 pieces of GAL20V8B chips in 28-pin PLCC package. Due to size constraints, soldering the chips is best done by hot air or hot plate, either using solder paste or tinning the pads and using flux. Fuse map is the same as in DIP-version. In the middle of the board there is a footprint for 0603 (optional) bypass capacitor, 0.1-0.22uF.
The version using DIP-chips can be found here: https://www.pcbway.com/project/shareproject/Commodore_64_PLA_replacement.html
More information, and Fuse-maps can be found from Daniel's website: http://www.freepascal.org/~daniel/c64pla/
Commodore 64 PLA replacement
*PCBWay community is a sharing platform. We are not responsible for any design issues and parameter issues (board thickness, surface finish, etc.) you choose.
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I used my TL866 with PLCC adapter that came with my TL866-kit. Separate adapters are also available for example in Aliexpress.
i Have TL866 and PLCC adapter too, and before buy the PCB i wanted program gal20v8b. i bought two dozen chips from two different aliexpress retailers, but not a single chip seems to work... was i particularly unlucky?
it must be TL866 II... i use T56.. but my TL866 II works also,, do you know the brand of the chips.. i bought Altera chips ... they didnt work in none of my programmers
I solved it by building the adapter from scratch. The one bought on aliexpres, although the position of the pins was correct, the connections and soldering were of poor quality and something went wrong.
Nice to see you got it solved. I've had varying success with those cheap Aliexpress adapters as well, I also swapped the socket to quality one from my adapter and it's been working perfectly ever since.
Hi , on which Assy do your PLA work?
On all long boards: Assy 326298, 250407, 250425, 250466 and KU-14194HB. It of course does not work on short boards, 250469, because they have the big 68 pin PLA.
Personally I always populate it reduce power ripple, but as it's optional, it's not strictly necessary as there is also bypass cap on C64 board near PLA.
Yes, it has been tested with 407, 425 and 466 extensively. Functionally this is identical to Daniël's through-hole version. What speed grade GAL20V8 did you use and which fuse map files?
Hi Jari, i use GAL20V8B-25LJ , speed grade 25ns. I have use the 2 Map files from freepascal.org for left and right gal. I have also tested the alternative files for the left one(booth).
Then there is something weird going on, I have used both 15 and 25 speed grade GALs and 407, 425 and 466 board assemblys and everything has just worked correctly. Could it be soldering issue? Also note that 407 assy has SID and PLA "swapped" compared to other boards.
I re-soldered the board without a PLCC socket, and the PLA worked immediately. I suspect the issue was with the contact resistance between the socket and the chip (perhaps some flux got in there). In any case, it's working now. Thanks!
Nice to hear you got it working 👍