Hey folks - I need people's opinion on something. I'm trying to chase down a possible issue with the analogue settings for my 10G ethernet setup using an Arria 10 board so have gone back to the Tranceiver Toolkit to try re-tuning the links to make sure I'm in the center of the eye. I have a length of fiber connecting port A tx to port B rx, and port B tx to port A rx.
Here's a summary of what I'm observing:
- When either direction is running on it's own, I get 0 bit error rate
- When both directions are running simultaneously, I get 0 bit error rate
- When one direction is running and I start the other direction, I bet 0 bit error rate on either
- When both directions are running but I stop one of them, the other one will see ~10^4 bit errors and then go back to no more errors
Obviously, it's the last one that is concerning but I'm not certain if it's something I truly need to worry about. So, opinions please. Is this just some weirdness with the PRBS generator stopping and it's all an internal issue to the FPGA that I won't see when not using the PRBS? Or have I been sold a badly designed board that has actual cross-talk problems?
As I understand it, you observe some bit error issues when two XCVR links in toolkit is running and then you stop one of the link. Since the other 3 cases, there is no issue, and also the bit error auto recover to BER = 0 without resetting, I believe this might be due to some weirdness with the XCVR toolkit like you said. If there is an actual BER, it would not recover to 0 and instead will keep on accumulating.
Please let me know if there is any concern. Thank you.