Question:
If the RMII interface is provided to the physical transmission medium (PHY) and this provided a reference clock to the MAC (that is integrated into the microcontrollers) and operated at a tenth of the expected speed (i.e. 5MHz), would everything still work (the data communication system is intended to operate as 10Mb/s Ethernet, but at reduced data rate of 1Mb/s)?
Answer:
Running at a slower reference clock should still work, however it is not guaranteed