DS90UB926Q-Q1: Will CRC error cause forward channel video quality issue ?

Hi,

CRC errors could indicate issue with signal quality and hardware. Could you tell us what the CRC error count showed? 

Could you read the CRC errors registers repeatedly?
Is there a continuous gradual increase or a sudden burst of CRC errors?
You could set up to read repeatedly at regular intervals to check the error count, and share if it's a high error count and if the registers reach max.


Best regards,
Ikram

Hi Ikram,

Yes, we could read CRC errors registers repeatedly and the reading value is continueously increase and finally reach max.

Though the CRC errors continuously increase and reach max, however the video is good we did not see any abnormal.

So we are woundering is CRC error only indicate the back channel quality but not thing to do with the forward channel ?

Hi PYTsai,

The CRC errors here are for forward channel data. Could you share from the tests the CRC errors count vs time. Then we could figure how fast it increases.

Best regards,
Ikram

Hi Ikram,

which DS90UB926 register can i read to read back the forward channel CRC error counts? thanks!

CRC Errors accumulate to 11,000 per second , keep on 11,000/per second even we reset the counter !

Hello,

Are you reading this from the 925 0xA- 0xB registers?

If possible can you try the BIST sequence as described in the 926 datasheet?

Can you also tell me more about this. Are these both custom designed boards (for SER and DES)? Have these been tested before? How many systems were tested and how many show this issue?

- Ikram

Hi Ikram,

Yes, my customer is reading 925 0xA- 0xB registers for CRC error. Does this register also reflect the forward channel's CRC error ? the datasheet said it is for back channel CRC.  

Yes, these both are customer design boards SER and DES. And my customer are uisng coaxtial way (single end) to connect 925 and 926. 

My customer had tested thousands of PCB and around 10% see the 925 0xA- 0xB registers for CRC error accumulate very fast, hower the 926 lock and pass signal are stable and video looks ok. 

Yes, we will try BIST sequence, the 926 datasheet only mentioned we can monitor the PASS output pulse to count to determine the payload error rate. Is this PASS out error rate for forward channel error ? Do we need to read any 926 register for forward channel error ?

Hello,

The SER 0xA - 0xB registers are for back channel CRC errors only. Other than the errors, is there any issue (relating to video, or I2C, etc) that you are observing in the system?

Can you please try this on the boards that show the error: https://www.ti.com/lit/ug/snlu243/snlu243.pdf

Please give me 1-2 days to check what next steps you can try here.

- Ikram

Hello,

PYTsai said:

And my customer are uisng coaxtial way (single end) to connect 925 and 926.

The 925 and 926 do not support coax (single-ended) connection. They only support STP differential connections. 
Although the video seems stable, using coax connection here is not recommended.

- Ikram