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CLa_R's avatar
CLa_R
Icon for Occasional Contributor rankOccasional Contributor
4 years ago
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FPGA Clock Pins

Hi to all! I'm working with a MAX10 FPGA (10M40SCE) and I would like if I can use the pins marked as CLKx[p/n] as normal (bidirectional) I/O pins. What is the default clock pin for supp...
  • sstrell's avatar
    sstrell
    4 years ago

    They're inputs when they're used as clocks. When not used a clock, they are GPIO (input or output).

    Just try connecting them in the Pin Planner and perform an I/O Assignment Analysis. This will verify that you are using the pins correctly.

CLa_R's avatar
CLa_R
Icon for Occasional Contributor rankOccasional Contributor
4 years ago

I read here at page 4:

Intel® MAX® 10 FPGA Device Family Pin Connection Guidelines

"Dedicated global clock input pins that can also be used for
the positive terminal inputs for differential global clock input
or user input pins. When these clock input pins are used as
single-ended pins, you can disregard the p notation.
CLK[0..7]p pins can function as regular I/O pins. "

What does it mean?

It is said that if the clock pin is not used as a dedicated pin, it can be used as an INPUT pin.

In the next sentence, it says it can function as a regular I/O pin.

But doesn't "I/O" mean Input and Output?

  • sstrell's avatar
    sstrell
    Icon for Super Contributor rankSuper Contributor
    4 years ago

    They're inputs when they're used as clocks. When not used a clock, they are GPIO (input or output).

    Just try connecting them in the Pin Planner and perform an I/O Assignment Analysis. This will verify that you are using the pins correctly.

    • CLa_R's avatar
      CLa_R
      Icon for Occasional Contributor rankOccasional Contributor
      4 years ago

      Okay, I tried to create two bidirectional signals and assigned them to two clock pins in pin planner.

      After compiling the project I have no errors.

      But I'm still dubious, can I rest assured that it works on real hardware?

      • sstrell's avatar
        sstrell
        Icon for Super Contributor rankSuper Contributor
        4 years ago

        Quartus wouldn't let you compile the project successfully if it wouldn't work in hardware.