STM32F439 Ethernet Frame Transmit Jitter

[stevehong]

Hello,

I have some questions regarding Ethernet frame transmission.

1) When is the value of the "ETH_MMCTGFCR" register increased?

After calling the "HAL_ETH_TransmitFrame()" function, I noticed that the value of the "ETH_MMCTGFCR" register increased in just under 1 millisecond. Could you please inform me about when the register is increased? Is it incremented after the frame is transmitted to the PHY?

2) After transmission, is there a possibility of approximately a 20 ms delay in the receiver?

I have verified the timing using Wireshark. I have configured my device to send an ETH frame to my laptop every 128 ms. The value of the "ETH_MMCTGFCR" register increases in less than 1 ms after calling the "HAL_ETH_TransmitFrame()" function. However, when I check the received time of the packet in my laptop with Wireshark, I observe occasional jitter. I have also attached the screenshot.

Thanks.

 

 

 

[Roger SHIVELY]

Hello @stevehong ,

There has been a case created to resolve this question and we will be reaching out to you directly.

Regards,
Roger