DP83640: DP83640 - Review schematic RMII mode

Hi Jiri,

Thanks for your query - please allow me some time to review the schematic and share feedback.

I should have comments for you by Wednesday at the latest.

Best regards,

Evan

Please see my feedback below:

• Adjust R11, R12, R13, R14 to 49.9 +/- 0.1% ohm
• Device is strapped into auto-negotiation enable for all speeds, looks good
• Device is strapped into RMII master mode, ETH_CLK is assumed to be 25M clock
• Is CLK_OUT being used? I see GPIO1 is strapped high to enable CLK_OUT, but CLK_OUT is not connected
  • In RMII master mode, the default here is a 50M reference clock output
• How is PTP sync being implemented on the system-level? GPIOs can be used to send SFD interrupts / time stamps to MAC

Please refer to this app-note for guidance on implementing IEEE 1588 time stamping:

https://www.ti.com/lit/ta/ssztau5/ssztau5.pdf

Thank you,

Evan

Hi Evan,

thank you for your review. And here is my answer to your questions.

• Adjust R11, R12, R13, R14 to 49.9 +/- 0.1% ohm - OK
• Device is strapped into RMII master mode, ETH_CLK is assumed to be 25M clock - YES
• Is CLK_OUT being used? I see GPIO1 is strapped high to enable CLK_OUT, but CLK_OUT is not connected - NO. But I update the schematic and you can see that the GPIO1 is not connected.
• How is PTP sync being implemented on the system-level? GPIOs can be used to send SFD interrupts / time stamps to MAC - I don't know. What is recommended?

Thank you for this PDF. It is very important. https://www.ti.com/lit/ta/ssztau5/ssztau5.pdf

Here is my update schematic: https://jumpshare.com/s/TkoIiX4sHhdrJyIqMUc8

Hi Jiri,

I cannot view the updated schematic, please attach as a PDF here.

For PTP sync design, it will depend on the capabilities of the stm32h723. Generally, I recommend routing at least 2 GPIOs from the PHY to MAC. These can be configured as PTP/SFD interrupt pins.

Thank you,

Evan

PDF with schematic is attached. Which GPIOs need to be connected to the MCU to get everything ready? In datasheet is written: Note that GPIO assignments are not exclusive.

So can I use: GPIO8 and GPIO9 for this?

8182.eth.pdf

Hi Evan,

thank you for your time and have a nice day.

Jirka