RGMII : ENET_REF_CLK

[eishishibusawa]

Dear Sir

Customers use the i.MX6DL ENET with RGMII.

Please tell me about RGMII I/F.

The following explanation is on P146 of IMX6SDLIEC Rev.8.

ENET_REF_CLK is used as a clock source for MII and RGMII modes only.

RGMII mode uses either GPIO_16 or RGMII_TX_CTL as a clock source.

For more information on these clocks, see the device Reference Manual and the Hardware Development Guide for i.MX 6Quad, 6Dual, 6DualLite, 6Solo Families of Applications Processors (IMX6DQ6SDLHDG).

I confirmed the Table 23-1. ENET External Signals (P1062) of IMX6SDLRM Rev.4.

ENET_REF_CLK : In RMII mode, this signal is the reference clock for receive, transmit, and the control interface.

(It seems that the ENET_REF_CLK is used only when the MII setting.)

Q1.

Does it need the 125MHz clock to ENET_REF_CLK when it is configured the ENET as RGMII?

Q2.

How is the AC spec (Duty) if it needs the 125MHz clock to the ENET_REF_CLK?

Best Regards,

Eishi SHIBUSAWA

[gusarambula]

Hello Eishi SHIBUSAWA,

To answer your first question RGMII does require a 125MHz clock externally provided.

You can find more details regarding this on Table 2-9 of the i.MX6 Hardware Design Guide.

As for the duty cycle the recommendation is to use good (25-50 ppm) frequency stability and 45%~55% & duty cycle clock source.

I hope this helps!

Regards,