I want to connect MAC available on STM32F745 to KSZ8041FTL (PHY) via RMII.

I will clock PHY from external 50MHz clock generator, connecting clock to the REFCLK input of PHY.

But what about STM32? Should I also connect 50 MHz clock to the STM32? If yes then I guess I should connect it to the RMII_REF_CLK input (PA1)?

Can I just connect output of the clock generator to both IC?

  • \$\begingroup\$ Yes.. In RMII mode, you have to provide same clock to both Micro and PHY Chip. \$\endgroup\$ – Swanand May 15 '17 at 3:55

Looking at the datasheets you provided, if you want to use RMII mode there seems to be no other alternative than what you already suggested. Namely, you must connect 50 MHz clock output both to PHY (REFCLK) and MAC (RMII_REF_CLK) in order to synchronize them.


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