Why is GMII designed for STM32MP dev kit?

[DMårt]

Hi!

I notice something!

In the devkit of STM32MP15xxxx, I found that ETH_TX_EN is used for GMII, but when I check the CubeMX, I found that RGMII is used instead.

 

This is the settings for RGMII. In the devkit schematics, it is ETH1_TX_EN, not ETH1_TX_CTL.

RGMII can only be selected as a mode. 

 

 

This is the timing diagram for GMII and RGMII. The difference is that GMII has ETH_RX_ER and RGMII does not. And also ETH_TX_CTL is used in RGMII and in ETH_TX_EN is used in GMII.

 

Question:

 

Can it be that STM32MP15xxxx devkit schematic is using ETH_TX_EN as label for ETH_TX_CTL for RGMII?

 

Also, there should be no pull-up resistor on ETH_MDC! Only ETH_MDIO.

[PatrickF]

Hi @DMårt 

Agree there is a typo in the signal naming inside the schematics. Should be read as ETH_TX_CTL as we are using RGMII.

Regarding the pull-up on MDC, it is just a good HW designer habit to avoid potential unwanted input toggling as signal is left floating until IO is initialized by the SW .