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Explorer
Explorer
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Registered: ‎02-19-2018

What is the MGT reference clock frequency when using the FMC GT clock?

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I am using the VC707 board to transmit data over the MGTs on the FMC connector. I am pretty new to this but so far I have discerned that the FMC itself has an oscillator that provides the reference clock for the MGT. Consulting UG885 tells me that this clock is on pin A9/A10. However, no where can I find what the frequency of this clock is. The GT Wizard wants to know what the reference clock frequency is for my specified line rate. There are many options, and since my reference clock is coming from the FMC I would think that I would just select the frequency that the FMC provides, but I am unsure how to find out what that is.

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Mentor
Mentor
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Registered: ‎02-24-2014

What is the daughter board you have connected to the FMC?    The documentation for this should give an idea of that the MGT Reference clock frequency will be.   Many FMC daughter boards have a programmable clock generator that can generate different reference clocks, and are programmed by an I2C interface.

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Mentor
Mentor
921 Views
Registered: ‎02-24-2014

What is the daughter board you have connected to the FMC?    The documentation for this should give an idea of that the MGT Reference clock frequency will be.   Many FMC daughter boards have a programmable clock generator that can generate different reference clocks, and are programmed by an I2C interface.

Don't forget to close a thread when possible by accepting a post as a solution.

View solution in original post

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Explorer
Explorer
657 Views
Registered: ‎02-19-2018

Ah I see, so the frequency of the clock isn't fixed but actually comes from the daughter board. That makes sense. I will consult the documentation for our board then. Thanks for your help.

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