TUSB321: The DIR pin changes from High to Low when data rate changes from USB3 to USB2, how to solve it ?

can you share your schematic?

Please refer to Annex

Hi Brian,

Would you check the schematics that my customer posted above? thanks!

it's DFP or UFP? from PORT pin, it seems UFP. but you mention DFP on current mode pin

Our product is Device so it is UFP

when CC1 is high, DIR is high. When CC2 is high, DIR is low

Hi Brian Zhou
Are you talking about a problematic situation? This situation is the situation when USB2.0 is connected

The general situation looks like
when CC1 is high, DIR is Low. When CC2 is high, DIR is High

Hi Brian Zhou
Add that CC1 is very easy to connect to USB2.0

CC2 is not so easy to connect to USB2.0

you mentioned data rate changes will cause DIR changes.. How do you changes datarate? change cable side?

No, I think it will become connected to USB2.0 when it cannot be connected to USB3.0

This is because of DIR pin status changes

DIR is just changing channel of USB3 mux, either TX1/RX1 or TX2/RX2 should work.

DIR must be in the right state regardless of CC1 or CC2, otherwise the speed will be reduced to USB2.0

May I have your email so we can talk in email?