DS280DF810: PRBS-31 error between Re-timer and ASICS

AMAN BANOLIA

Part Number: DS280DF810

Hello,

I am running unframed PRBS of data-rate 111.81 Gbps from the analyzer over 4 lane @27.9525 Gpbs as shown in the image with serdes loopback at the receiver. We have done the re-timer RX setting to Adaptive Mode 2 for both retimer.

We have the following observation.

1. PRBS is running ok between QSFP-28 to Retimer and from Retimer to QSFP-28

2. PRBS error is detected between ASICS and Retimer

We have the following query

1. Does multiple Retimer in the path can create an issue?

2. Does the CAL_CLK_IN clock have and role in the error?

3. How to calculate and set Pre and post-emphasis to correct the PRBS errors

Regards,

Aman

over 1 year ago

Lucas Wolter over 1 year ago

TI__Mastermind 23905 points

Hi Aman,

AMAN BANOLIA said:
1. Does multiple Retimer in the path can create an issue?

Since retimers reconstruct the high-speed signal, having multiple retimers in the path shouldn't create any issues.

AMAN BANOLIA said:
2. Does the CAL_CLK_IN clock have and role in the error?

As long as CAL_CLK_IN meets these datasheet specs, I don't expect it to be a root cause of the errors.

AMAN BANOLIA said:
3. How to calculate and set Pre and post-emphasis to correct the PRBS errors

I recommend conducting greenbox testing to determine optimal TX FIR parameters. This app note explains the testing methodology.

https://www.ti.com/lit/an/slyt678/slyt678.pdf?ts=1703709168760&ref_url=https%253A%252F%252Fwww.google.com%252F

If the issue persists after adjusting the TX FIR parameters, can you share full register dumps from both retimers for me to review?

Best,

Lucas

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DS280DF810: PRBS-31 error between Re-timer and ASICS