DS90UB940-Q1: RXIN has signal when it didn't connect serializer

Kailyn Chen

Part Number: DS90UB940-Q1

Hello,

The customer used DS90UB940-Q1 which didn't connect serializer, when 940 power up according to the power up sequence, the registers are all default configuration, lock and pass pin are both low, but the RXIN has signal like below:

Why the RXIn has input signal even though it didn't connect serilaizer?

Best regards

kailyn

over 2 years ago

+1 Logan Cummins over 2 years ago

TI__Guru 66840 points

Kailyn,

FPD is full duplex, so 940RX has a back-channel component that it over-layed in upstream direction. That is what is being observed here.

Regards,

Logan

0 Kailyn Chen over 2 years ago in reply to Logan Cummins

TI__Genius 9560 points

Hi Logan，

Thank you very much for your reply, do you mean it is normal of RXIN has signal even though it has no input? About back-channel component that it over-layed in upstream direction, could you please describe it in detail?

Best regards

kailyn

+1 Logan Cummins over 2 years ago in reply to Kailyn Chen

TI__Guru 66840 points

Hi Kailyn,

FPD-Link is a full-duplex communication. Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time.

Thus, DES broadcasts the Back-Channel signal, and SER broadcasts the Forward-Channel signal.

Regards,

Logan

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DS90UB940-Q1: RXIN has signal when it didn't connect serializer