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Discussion in 'Electronic Components' started by Guest, Aug 20, 2004.

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  1. Guest

    Guest Guest

    GAL,PAL,PLD, CPLD,FPGA, (what else...?)

    GAL : Generic Logic Array
    PAL : Programmable Array Logic
    PLD : Programmable Logic Device
    CPLD : Complex Programmable Logic Device
    FPGA : Field Programmable Gate Array

    Can someone explain with comparison what is the difference between all these
    GAL,PAL,PLD, CPLD,FPGA, (what else...?) logic units?

    Can all these units can be programmable with VHDL ?
  2. I thought this was: Gate Array Logic.
    That's a language. As long as someone has a tool to convert VHDL source
    code to the device's expected "bit" file then yes.
  3. Roland Macho

    Roland Macho Guest

    As a long year digital expert I'll try to tell you the difference of all
    these logic parts.
    First: the content of all of them can be described by the language VHDL.
    But this makes sense only with higher complexities, which big CPLDs and
    FPGAs have.
    PLDs, PALs and GALs are the lowest complexity of logic arrays (f.e.
    22V10 -> 10 Flip-Flops + AND/OR-Logic).
    CPLDs and FPGAs have more gates and Flip-Flops, where CPLDs have a more
    fixed structure (predefined number of gates and FFs) , while FPGAs are
    consisting sometimes of pure gates (ACTEL, Antifuse) and can be handled like
    true gate arrays. FFs are built by gates then.
    For the high complexities VHDL is the right tool to handle big designs.
    But you should keep in mind, that the later layout of the FPGA-chip depends
    on the design (how many IO-ports, number of FFs, number of gates, number of
    logic blocks etc.).
    The best way to learn about the digital designs is to use the partly free
    tools and do a design by yourself.
    All suppliers have nice kitparts and offer design software .

    Have fun.

  4. Guest

    Guest Guest

    Dear Roland,

    Thank you for your clear and easy to understand summary.
    Can you recomment a particular one to learn CPLD/FPGA and VHDL?
  5. Leon Heller

    Leon Heller Guest

    I have a simple CPLD design on my webs site that may be used with the free
    Xilinx Webpack software.

  6. Guest

    Guest Guest

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