UB941/0 reset

Ryan Wang

Part Number: DS90UB940-Q1

Dear expert,

My system is UB941 + UB940. I find if reset UB940 with PDB, everything is OK after re-lock. But if reset UB941 and then re-lock, there are some CRC error for the first 2048 bytes video data received by screen. The data afterwards are OK.

I saw below description for UB940 datasheet for Power Sequence. So this phenomenon is normal in theoretical? But UB941 send video data after LOCK is detected. Why there is still CRC error?

"Provide valid data from a compatible Serializer before power-up or apply reset"

And there is error also for the first frame SPI data which is also sent after LOCK is detected. Is it normal?

Thanks

over 4 years ago

0 Ryan Wang over 4 years ago

TI__Expert 7475 points

Dear expert,

After UB941 reset, UB940 has to be reset? Or can just wait for some period to get stable communication? And how long should wait?

Thanks

0 Ryan Wang over 4 years ago in reply to Ryan Wang

TI__Expert 7475 points

Dear expert,

I just did experiment. I wait for more than 10min after LOCK detected. But both video data and SPI data for the first frame still have error.

0 Ben Dattilo over 4 years ago in reply to Ryan Wang

TI__Mastermind 25765 points

Hi Ryan,

While the SER is powered down and the DES is still active, the DES will try to lock onto a signal that is not present (noise since there is no SER). The SER needs to be powered on and connected to the DES before the DES is powered on so the DES can lock directly onto the SER. Otherwise, as you have observed, the DES will be searching and may take a while to lock on to the SER.

In short: if the SER is reset, the DES should also be reset.

Regards,

Ben

0 Ryan Wang over 4 years ago in reply to Ben Dattilo

TI__Expert 7475 points

Ben,

Thanks for feedback

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UB941/0 reset