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iMX6q RGMII back to back connection with FPGA

Question asked by Karthikeyan Subramanian on Jun 27, 2013
Latest reply on Aug 1, 2013 by Karthikeyan Subramanian
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In our custom board we have RGMII back to back connection between i.MX6Q and Zynq FPGA.

The Ethernet reference clocks (125Mhz) on both the processors are driven by different sources.

We have taken care of the driver changes to fake the presence of PHY and we have confirmed by probing all the signals.

During the signal analysis, we notice non-skewed tx_clk-tx_ctl and rx_clk-rx_ctl signals at imx6 end during the data transfer.

Both rx-clk and tx-clk are at 25Mhz (for 100M).

While connecting i.MX6 to the external PHY (instead of back to back RGMII) the skew settings on the PHY are mandatory for successful communication.

So, we feel that skewing would be required to get over this.

How can the skew be adjusted in case of the back-back connections? Does i.MX6 have internal skew settings which can be adjusted to meet our requirement?

Is there anything else we need to look at?