DS90UB940-Q1: 927 /940 LOCK

Betty Guo

Part Number: DS90UB940-Q1

Hi team,

customer use 927 pair 940 in the case. for the 940, the hardware of MODE_SEL1 set to 20Mbps STP input mode.

Since the 940 datasheet, if 940 pair 927, the back channel speed should be set to 5Mbps. we want to know how to change the back channel speed to 5Mbps without hardware change?

If use 20Mbps, 940 lock is low. customer tried to change hardware of MODE_SEL pin to 5Mbps, LOCK is high. they have builded 20pcs board, can't change hardware now, so asking how to change back channle speed to 5Mbps by software.

thanks.

over 4 years ago

0 Aaron Heng over 4 years ago

TI__Mastermind 37350 points

Hi Betty,

I need to investigate this. I will get back to you by end of this Friday.

Aaron

0 Aaron Heng over 4 years ago in reply to Aaron Heng

TI__Mastermind 37350 points

Hi Betty,

I would like to inform you that I wasn't able to get the response by today. I'm sorry for any inconvenience. I will get back with you by next week on Wednesday.

Aaron

0 Aaron Heng over 4 years ago in reply to Aaron Heng

TI__Mastermind 37350 points

Hi Betty,

In order to process and expedite the investigation, I need your help to read the revision ID (register 0x13) as well as take the top marking photo. Thanks.

Aaron

0 Aaron Heng over 4 years ago in reply to Aaron Heng

TI__Mastermind 37350 points

Hi Betty,

I dug in the issue in depth, and found overriding the strap mode shouldn't be issue. The register 0x23 of the 940 device mentions about the 0x32 register. Please do not set this to a different value. Changing the value of this register will not put the device back channel in the correct timing. If you want to override the strap from 20Mbps to 5Mbps, all you need to do is change the following item below. This is also described in section 7.3.8.2 Back Channel Configuration.

Set BC_HIGH_SPEED = 0 on the 0x23 register.
Set BC_FREQ_SELECT = 0 on the 0x23 register.
If you are using 927, you will need to set the register 0x03[5] selecting the auto-ack operation. If this bit is not set, you will get the automatic acknowledge, and the I2C bus can be hung for while.

Hope this helps. Let me know if you have any questions.

Aaron

0 Betty Guo over 4 years ago in reply to Aaron Heng

TI__Expert 7300 points

Thanks Aaron, I will let customer to try it.

0 Steven(Shenzhen) Shi over 4 years ago in reply to Betty Guo

TI__Mastermind 30515 points

If you have any udpate, pls let's know.

btw, your part number is 940 or 940N?

regards,

Steven

0 user6323992 over 4 years ago in reply to Steven(Shenzhen) Shi

Prodigy 10 points

I’m customer.

Use the part number is DS90UB940TNKD*Q1

regards,

HaoChuncheng

Interface

Interface forum

DS90UB940-Q1: 927 /940 LOCK