iMX7D clock for second Ethernet/RGMII

Technical Support
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Hi!

I’m designing a carrier board for iMX7D modules that will have a second ethernet port using the gigabit PHY KSZ9031/9021 connected via RGMII.

There is an issue with the main oscillator on the modules, as described here: Offset in main oscillator in imx7d - Technical Support - Toradex Community

According to iMX7 ref. manual from NXP, it seems possible to have the reference clock for ENET2 from a couple of pins, including EPDC_BDR0:

[upload|VXg1sqRBcgBwvToXz1XHQke8R0o=]

But using the Toradex Pinout Designer, it is not possible to select any pin as the reference clock for the ETH 2 MAC using RGMII, only using RMII:
[upload|ss9+IWmUQ+t2a/QNyNy2IkIIRHM=]

So my question is: Can I use the PHY’s generated 125MHz on the pin 106 of the SOM as ref. clock for the second ethernet?

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Hello @brunoaa and Welcome to the Toradex Community!

There is an issue with the main oscillator on the modules, as described here: https://www.toradex.com/community/questions/38539/offset-in-main-oscillator-in-imx7d.html

Yes, that’s true.

But using the Toradex Pinout Designer, it is not possible to select any pin as the reference clock for the ETH 2 MAC using RGMII, only using RMII

There is no need of Reference Clock for RGMII, only form RMII.

So my question is: Can I use the PHY’s generated 125MHz on the pin 106 of the SOM as ref. clock for the second Ethernet?

No, you don’t need to do this. The synchronization is done over TXC and RXC signals.

Best regards,
Jaski

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Hi Jaski,

You’re right!

Thank you for your support!!

4

You are welcome. Thanks for your feedback.