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i.MX6 RGMII internal reference clock 125MHz

Question asked by Mathias Neusch on Feb 5, 2014
Latest reply on Aug 5, 2014 by Dan Kessler

I would use the internal clock for RGMII. The external Switch have no clock reference, because the 12 wire RGMII interface dont't support that.


configuration clock: (like Hardware Development Guide)


CCM_ANALOG_PLL_ENETn                        - 125MHz

ENET_CLK_SEL                                         - get enet tx reference clk from internal clock from anatop (loopback through pad), this clock also sent out to external PHY




It is possible to use ENET_REF_CLK(pad) then as GPIO ?    (IOMUXC_SW_MUX_CTL_PAD_ENET_REF_CLK)




I found this diskussion:




Fei Liu        21.05.2013 19:54        

In RGMII Mode, only the pin "ENET_REF_CLK" could used as 125M reference clock input.

The 125M reference clock could be from PHY chip, or external oscillator, and could also be routed from GPIO_16(need software configuration).     also?


In RMII Mode, only two pins "GPIO_16" and "RGMII_TX_CTL" could be used as the 50M reference clock. The clock source could be from external oscillator or internal PLL, need software configuration. Please refer the document "I.MX6 Hardware Development Guide", Chapter 11



It is possible to use the internal PLL 125MHz for RGMII without external PHY or external oscillator ?

So the workaround GPIO_16


it's confusing to me