STM32H753VIH6 RMII Validation

[Ramesh_pb]

Hi ,

We are facing an RMII signal setup time violation on the RX side of the RTL8364.

We have already discussed this issue with the Realtek team, and they have suggested verifying the STM controller side, as the timing issue may be originating there.

Could you please review the issue and suggest a possible workaround or any recommended configuration changes on the STM controller side to resolve this setup time violation?

For your reference, we have attached the schematics and waveform captures.

Looking forward to your guidance.

 

Thank you.

[mƎALLEm]

Hello, ​@Ramesh_pb and welcome to the ST community,

Just need to validate my understanding of your request.

The datasheet provides the following data:

The setup time is measured in between the rising edge of RXD[1:0] and the rising edge of the clock and the minimum setup time is 2ns/1.5ns.

But in the screenshot you’ve shared you are measuring the setup time in between the falling edge of the clock and the rising edge of RXD[1:0].

Could you please clarify? or Am I missing something?

 

[Ramesh_pb]

Hi,

 

Q: The setup time is measured in between the rising edge of RXD[1:0] and the rising edge of the clock and the minimum setup time is 2ns/1.5ns.But in the screenshot you’ve shared you are measuring the setup time in between the falling edge of the clock and the rising edge of RXD[1:0].

A: According to the RTL8364 datasheet, the RX setup time should be measured from the falling edge of the clock to the rising edge of the RXD signal.

 

For your information, the RXD signal refers to the RTL8364 which corresponds to the TXD signal on the STM side. However, the STM datasheet does not provide any setup time specifications or timing characteristics for the TXD signal. Could you please clarify how we can verify that the STM controller meets the setup time requirements specified by the RTL8364?

 

Please find the attached RTL8364 timing requirements datasheet for your reference.

 

 

Thanks

[mƎALLEm]

Ok now I understood.

We don’t provide TxD setup time. The setup time values are only provided for inputs. Theoretically, RTL8364 is compatible with the Ethernet MAC RMII as TxD maximum Output valid is 11ns.

Now regarding the screenshot you shared, indeed there is an issue. As said by ​@LCE did you set the GPIO to a maximum speed?

[LCE]

> RX side of the RTL8364

I don’t know the N6 - but are the ETH TX GPIOs set to maximum speed?

Maybe reducing the serial resistors might help.

PCB layout has same lengths for all relevant tracks ?

[mƎALLEm]

​@Ramesh_pb 

Could you please state on this thread please? Did you solve your problem?