TUSB1210: voltage drop at turn around cycle

Yusuke Mukuno

Expert 7395 points

Part Number: TUSB1210

Hi expert,

My customer have an issue about voltage drop at turn around cycle.

Please refer the following waveform

ch1:clock

ch2:data

ch3:dir

They found the data signal voltage drop after DIR was Negated(turn around cycle).

Could you please let me know about the reason of this behavior and avoiding method.

Thanks

Muk

over 5 years ago

0 Brian Zhou over 5 years ago

TI__Guru**** 158105 points

this is expected, during turn around, either side driving the data.

0 Yusuke Mukuno over 5 years ago in reply to Brian Zhou

TI__Expert 7395 points

Hi Zhou-san,

Is it any problem?

Do you have any recommended solution?

Thanks

Muk

0 Brian Zhou over 5 years ago in reply to Yusuke Mukuno

TI__Guru**** 158105 points

no, it's not issue.

0 user6430127 over 5 years ago in reply to Brian Zhou

Prodigy 10 points

The UTMI+ Low Pin Interface Specification Revison1.1 says
"A change in dir causes a tunraround cycle on the bus during which, neither Link nor PHY can drive the bus."

0 Yusuke Mukuno over 5 years ago in reply to user6430127

TI__Expert 7395 points

Hi Zhou-san

Please give me your comment on the content of the ULPI Specification above.
What is the actual output of the TUSB1210 to the data bus during a turn around cycle?
(In particular, please tell us the device output status after the dir fall, and if possible, after the rise.)

・Drive High or
・Drive Low or
・Pull-up or
・Pull-down or
・High-Z?

Thanks

Muk

0 Brian Zhou over 5 years ago in reply to Yusuke Mukuno

TI__Guru**** 158105 points

it's more like High-Z state since no one is drive the bus.

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TUSB1210: voltage drop at turn around cycle