I've been playing about with FPGA's for a while now and my single most read blog post ever is this one entitled "FPGAs".
I really like the idea however of trying to get some 5V CPLD's into my C64 to do some more complex chip replacement. The only problem is that the ONLY manufacturer that is currently still manufacturing 5V CPLD's is Atmel (Yes yes I know Xilinx have a heap of stock left but they have actually ceased making them). So I wanted a chip that was good for new designs.
The big problem is that there is only one Dev board available, it's produced by Atmel in tiny quantities and it is really expensive compared to the cheap Chinese CPLD dev boards available for other manufacturers chips. This is where my search of the Internet found this little beauty (or ugly) on Instructables, the "Ghetto Programmable Logic (CPLD) Development System"
Version 0.1 - Getting it wrong
So initially I replicated the Ghetto board exactly and I used a footprint that I'd downloaded for the socket that I'd selected. On paper it looked fine. In reality I completely stuffed up the pin assignment for the the PLCC 44 pin socket. When importing the part into DipTrace, Library Loader did tell me to check the pin assignments, but assumed it would be fine . . . WRONG!
So here is the bad version 0.1 board and the correct PLCC 44 pin socket pin out.
Version 0.2 - Getting it right
I took the opportunity to do some proper research this time and along with the correct pin out for the socket I also reviewed the capacitor and resistors required against the schematic from Atmel's development board.
Here is the list of changes:
- Corrected PLCC44 pin socket pin out
- Added additional resistors to the JTAG header
- Added power header pins
- Re-routed the pins to be sequentially numbered
- Improved the silkscreen
- Correct Headers to 0.1"
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