Sometimes you can find a CPLD (Complex Programmable Logic Device) on a circuit board.

  • What can you do to find out what it is for?
  • What are the limits and capabilities?
  • What are common applications for a CPLD?

1 Answer 1


CPLDs are frequently used for glue logic. They are quite limited compared to FPGAs and implement a sea of gates design rather than more general LUTS found in FPGAs. Although that probably isn't always the case some CPLDs may be nothing more than a tiny FPGA with a built in ROM.

CPLDs usually have a built in ROM making them harder or near impossible to RE. Since there is no external configuration.

FPGAs are often equivalent to a million+ gates. Whereas CPLDs are at most in the tens of thousands of gates. They might be more accurately called Simple Programmable Logic Devices!

If there is no identification on the package you are going to have a hard time doing anything with it.

Though, sometimes its sufficient to see what is connected to the IO pins of the CPLD to tell what it is used for.


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