DS90UB948-Q1: BIST not working when enabling high-speed back-channel at 20Mpbs

Hi,

Do you mean you are setting register 0x23[4] to 1 on the 948?

Regards,

Michael W.

Hello Micheal,

Sorry for the confusion caused. Yes, setting 0x23[4] to 1.

Regards,
Mohamed

What steps are you doing to enable BIST, in both cases?

Hello Michael, 

1- D_GPIO0 pin strapped HIGH, D_GPIO[3:1] strapped LOW. 

2- Setting the BIST_PIN_CONFIG bit in the 0x24 register to 0  ( Bist configured through bits 2:0 in this register ) 
3- Selecting the BIST Clock source at the Serializer from the Deserializer (setting 0x24[2:1]  = 11)  enabling the BIST (setting 0x24[0]  to 1) .

Please note that the PASS is HIGH when I enable the back channel at 5Mbps. But it's not when the BC is  enabled at 20Mbps. 

Regards, 
Mohamed

When are you setting the BC to 20Mbps in your steps? Does the I2C between the 948 and 949 work when in 20 Mbps mode?