TUSB8040A / state of SS upstream signals

K.Yaita

Guru 29720 points

Other Parts Discussed in Thread: TUSB8040A

Hi Team,

My customer has a certain issue in his system currently and he is investigating the function of TUSB8040A.

Could you tell me the states of the following Upstream Signals when GRSTn is asserted?

Is my understanding correct that USB_SSTXP/M_UP(B39, A42) are both "L" level outputs and USB_SSRXP/M_UP(A44, B40) are both Hi-Z in this case?

Best Regards,

Yaita / Japan disty

over 10 years ago

0 Diego Cortes over 10 years ago

TI__Mastermind 36085 points

Hello Yaita-san,

Per USB spec this port shall be disabled at this point, however I am not sure about the actual implementation, let me ask my team to provide a precise feedback.

Best regards,

Diego.

0 K.Yaita over 10 years ago in reply to Diego Cortes

Guru 29720 points

Hi Diego-san,

Thank you for your support.

I will wait for the feedback from your team.

Best Regards,

Yaita

0 Diego Cortes over 10 years ago in reply to K.Yaita

TI__Mastermind 36085 points

Hello Yaita-san,

The SS upstream port is a differential port, which is disabled during reset operation, therefore the TX pair would be in an undetermined state, meanwhile the RX pair shall have its far end termination disabled (50 Ohms).

Best regards,

Diego.

0 K.Yaita over 10 years ago in reply to Diego Cortes

Guru 29720 points

Diego-san,

I understood as the following.

- USB_SSTXP/M_UP(B39, A42): undetermined state

- USB_SSRXP/M_UP(A44, B40): internal termination disabled(equivalent as Hi-Z)

Thanks for your support.

Best Regards,

Yaita

0 K.Yaita over 10 years ago in reply to K.Yaita

Guru 29720 points

Diego-san,

May I ask the additional question?

>the RX pair shall have its far end termination disabled (50 Ohms).

Is the above "termination resistor(50 Ohms)" same as the the "R_Term" in Figure 6-23(page.177) of Universal Serial Bus 3.0 Specification(Rev 1.0)?

http://www.usb.org/developers/docs/documents_archive/

Best Regards,

Yaita

0 Diego Cortes over 10 years ago in reply to K.Yaita

TI__Mastermind 36085 points

Hello Yaita-san,

You are correct, the R_Term is the far end termination resistor I mentioned.

Regards,

Diego.

0 K.Yaita over 10 years ago in reply to Diego Cortes

Guru 29720 points

Diego-san,

I appreciate for your support.

Best Regards,

Yaita

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TUSB8040A / state of SS upstream signals