Routing an External Clock to PSoC® via GPIO with PSoC Creator™ – KBA90459

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    Question: How can you connect an external clock to PSoC®? The PSoC’s-dedicated MHz oscillator pins appear to be used only for an external crystal. The oscillator of interest is in the 10–20 MHz range, can drive a CMOS load of 15 pF, and has a rise/fall time of 6 ns.




    To use an external clock source, please follow these steps:

    1.   Place a digital input pin in your top design.
    2.   Draw a wire from that pin and give a name to that net.
    3.   In the .cydwr window, go to Clocks tab and double-click Master Clock.
    4.   A window named Configure System Clocks will open. In this, check the Digital Signal and click on the Browse button.
    5.   Then select the net that you gave for the pin (clock input) previously and give the frequency and tolerance value.
    6.   Now you can use this clock to derive any clock source.

    For further information, please refer to the application note PSoC 3 and PSoC 5LP Clocking Resources.