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Observer geopa
Observer
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Registered: ‎10-30-2015

USB & Ethernet PHYs reference clocks through PS_MIO pins

Hello,

I need to support both USB3 and Gigabit Ethernet on a Zynq Ultrascale+ device. I verified that I can use in parallel GEM3 and USB0, without conflict on the MIOs.

Preferably I would like to clock both PHYs from the Zynq PS (PS_MIO 44 & 45, or other unused ones) and not from external oscillators. This means I need to generate 25MHz and 26/19.2MHz (for Ethernet and USB respectively) with max +-50ppm frequency tolerance and <100ps jitter.

I fail to find relevant information on if that's even possible. Do I miss something basic? I understand that the common case is to use external oscillators, but I would really like to avoid doing so if possible.

I repeat that I am not referring to the ULPI's input clock, or the RGMII's Rx and Tx clocks, but to the output reference clocks that clock the PHYs.

Thanks in advance,
Giorgos

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