T1014 Processor RGMII Ethernet Interface Question

[robertmartinson]

When using the T1014 processor, I understand that to use the RGMII gigabit Ethernet interface, a 125MHz clock needs to be applied to the EC1_GTX_CLK125 pin.  If a design only contains a 10/100 Base-T Ethernet PHY and I only desire to run the Ethernet interface at 100 Base-T, I assume that I would only connect a 25MHz clock to the EC1_GTX_CLK125 pin.  I cannot confirm this in any of the datasheets/application notes.  I need confirmation that this is acceptable.  Thanks! 

[ufedor]

Your assumption is incorrect.

Even if RGMII interface is used with 10/100 Base-T Ethernet PHY the 125 MHz reference clock has to be applied to the  EC1_GTX_CLK125.

Refer to the QorIQ T1024, T1014 Data Sheet, Table 19. ECn_GTX_CLK125 AC timing specifications.

[robertmartinson]

Thanks for the help.

When I connect 125MHz to EC1_GTX_CLK125, does this mean I will get a 125MHz clock output on the EC1_GTX_CLK pin or will this output be scaled down internally on the processor to 25MHz for use as an input to the 10/100 Base-T Ethernet PHY.

[ufedor]

Yes, it will be scaled internally in accordance with the selected data rate - i.e. 25 MHz for 100 Mbps and 2.5 MHz for 10 Mbps.