When disable 954 how about the DS90UB953 FC status

Part Number: DS90UB954

Hi TI Support Team

I want to know the 953 forward channel status when I disable 954 IC (signal PDB pull low ). 

Setup:

PC(ALP) =>USB2ANY(I2C) => 954 <=>FPDLINK(POC)<=>953

Step 1:

Power on: 954&953 linked.  I can find those info from ALP.  CSI-Sync mode; BC rata 50Mbps; Linked 100MHz; Pass Sts: Pass

Step 2: 

Setting the 954 register: 0x58 address from 5E to 0E (disable back channel),

Pull low PDB for 954 and the PoC power still working correct. 

Step 3:

Measure the 954 RIN+/- , probe@ AC coupling in 954 pin side. 

Result: I find the 943 forward channel working at abnormality status. because the waveform and eye diagram amplitude abnormal. Please find it in below. 

Question:

1. Because I want to measure the eye diagram at RIN pin, so I have to disable back channel in order to get correct signal. 

    But when 954 back channel disable that means 953 can't get reference clock from 954.

    What is the status for 953 in this case ?  Does it will output random data/signal for FPDLINK FC data? Please check the waveform. 

2. When I change 953 register 0x03 address from 0x48 to 0x5A ( Non-Syn with external clock) and I change 954 register 0x58 address to 0x5A (10Mbps back channel Non-sync compatibility) 

    Then disable 954 back channel. I can get correct 2Gbps FPDLINK FC data.  In this case, the FC datarate is 2Gbps and BC datarate is 10Mbps.   // 953 have one 25MHz osc. 

 3. When I change 953 register 0x03 address from 0x48 to 0x5B ( Non-Syn with internal AON clock) and 0x05 address bit 3 to 1

    Then I change 954 register 0x58 address to 0x5A (10Mbps back channel Non-sync compatibility) and disable 954 back channel. 

    I can't get correct 4Gbps FPDLINK FC data. Can you please check if i missing something ?

Case 1:

Case 1:

Thanks

Yutai