Схемы, платы, компоненты

https://en.wikipedia.org/wiki/Media-independent_interface#Signal_levels

The RMII signals are treated as lumped signals rather than transmission lines. However, the IEEE version of the related MII standard specifies 68 Ω trace impedance.[4] National recommends running 50 Ω traces with 33 Ω series termination resistors for either MII or RMII mode to reduce reflections.[citation needed] National also suggests that traces be kept under 0.15 m long and matched within 0.05 m on length to minimize skew.[4]: 5

 
Файл [4] на который выше ссылаеются, т.е. «AN-1469 PHYTER Design & Layout Guide» (TI Application Report)
прилагаю.

snla079d.pdf