32.5.1 Clocks

In RMII mode, the actual reference clock (GMAC_GREFCK), i.e., 50 MHz clock is an external signal.

In MII mode, there are two clocks, transmit clock (GMAC_TXCK) and receive clock (GMAC_GRXCK). These are 25 MHz clocks. Each one drives four signals in MII mode.

In GMII Ethernet protocol mode, there is a faster transmit clock (GMAC_GTXCK). This is from the system clock generator and operates at 125 MHz for gigabit operation. The RX clock must run at 125 MHz but uses the same RX pin (GMAC_GRXCK) as MII.