DS90UB926Q-Q1: BIST mode for DS90UB926Q-Q1

Dear Sir:

                 I follow below step to setup 926/927 for BIST mode , Then I read register 0x25 of 926  and  BIST ERROR count is 0x00 , I also check with PASS pin of 926, it have some wave as below picture(yellow line is PCLK and purple line is PASS pin). If it have no any error then PASS pin should always pull up , right? BTW , Can we used BIST mode to check connection and quality for cable?

Best Regard

Jason

Dear Sir:
Our step as below for BIST mode

1.Pull up Pin 44(BISTEN) of 926
2.Check 0x24 bit(0) = 1(BIST Enabled)
3.Check 926 0x14 bit(0)=1 (BIST Enabled)
4.Pull down Pin 44(BISTEN)of 926 and turn off BIST mode
5.Pass PIN(PIN42) is dropping low
6.Check 0x25 (BIST Error Count) of 926 and it=0x00

what's wrong for our step , do you have any suggest to us?

Best Regard
Jason