DP83TG720S-Q1: DP83TG720S-Q1 has crc errors when sending large packets

Cheng Chen

Part Number: DP83TG720S-Q1

Tool/software:

Hi,

We are using DP83TG720S-Q1 to interface 1G automotive ethernet with Xilinx MPSoC. The settings is RGMII interface. We always found there is crc error when transmitting large packet (for example 1400 bytes) constantly. Small packets seems fine (smaller than 900 bytes).

We did RGMII loopback and still see error indications. Any idea what causes the issue? Thanks

Che

over 1 year ago

0 Avtar Dhaliwal over 1 year ago

TI__Expert 4740 points

Hi Che,

Can you try changing RGMII timing? Specifically testing shift vs align as well as different shift levels. Furthermore, try increasing the IPG to help PHY clear quicker. Please double check to make sure PHY clock out is within spec as well as MAC's clock is within spec too.

Regards,

Avtar

0 Cheng Chen over 1 year ago in reply to Avtar Dhaliwal

Prodigy 40 points

HI Avtar,

Thanks for the reply. We are already in shift mode: the system only works with several shift levels. We tried the shift values. Some works better than the others (crc errors are less). Checked the clk and data line on the scope, which also confirmed the result: Some delays makes clock crossover data in the middle. But the crc errors still exist. IPG doesn't seem help. What's the spec for PHY clock and MAC clock. Any other thoughts? Thanks.

Regards,

Che

+1 Avtar Dhaliwal over 1 year ago in reply to Cheng Chen

TI__Expert 4740 points

Hello Che,

In section 6.6 the timing requirements have the information on the crystal or oscillator specs that need to be met, and the SOC should have their own spec similar to this. As for When you say some shift levels work better than others, is there a correlation between for instance more shift and less delays?

Regards,

Avtar

0 Cheng Chen over 1 year ago in reply to Avtar Dhaliwal

Prodigy 40 points

Thanks Avtar. It seems the issue was on the clock. PPM is not within the spec. Thanks for the suggestions!

Che

0 Avtar Dhaliwal over 1 year ago in reply to Cheng Chen

TI__Expert 4740 points

Hello Cheng,

You are welcome.

Regards,

Avtar

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DP83TG720S-Q1: DP83TG720S-Q1 has crc errors when sending large packets