Why is GMII designed for STM32MP dev kit?

DMårt · ‎2024-05-11

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.

STM32MP151AAC3 custom board with STM32-OS as operating system: https://github.com/DanielMartensson/STM32-Computer

PatrickF · ‎2024-05-13

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 .

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View solution in original post

PatrickF · ‎2024-05-13

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 .

In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question.