TUSB1044: DIR_SEL

David Mckinney

Expert 6820 points

Part Number: TUSB1044

Can I get some additional information on the DIR_SEL pins and what they do in setting the operational mode?

How are we supposed to use these registers?
What does it actually do?
When do we use it?
Why is it necessary?

over 4 years ago

0 Malik Barton57 over 4 years ago

TI__Guru 64326 points

Hi David,

DIR_SEL is used to select the device functional mode and and mapping. Please refer to Table 5. I2C Configuration Control in the datasheet to understand the how DIR_SEL in combination with CTLSEL and FLIPSEL to get the desired functional modes.

0 David Mckinney over 4 years ago in reply to Malik Barton57

TI__Expert 6820 points

Hi Malik;

"DIR_SEL is used to select the device functional mode and mapping", what does "functional mode" and "mapping" mean? We changed DIR_SEL and I don't see any measurable difference.

0 Malik Barton57 over 4 years ago in reply to David Mckinney

TI__Guru 64326 points

Hi David,

DIR_SEL changes between USB + DP Alt mode and USB + Custom Alt mode as well as Source and Sink modes. This changes the active paths for the device. What kind of behavior are you seeing? See Table 5. I2C Configuration Control and Table 4. INPUT to OUTPUT Mapping.

0 David Mckinney over 4 years ago in reply to Malik Barton57

TI__Expert 6820 points

Hi Malik;

Looking at Table 5, I would believe that the differences are very subtle and that they would be very hard to observe. Can you advise if there is anyway to observe these differences? Also, are the DIR_SEL value updated real time, or only on RESET or initial power up of the device. If they are changing the DIR_SEL settings, will they need to issue SW RESET in order to see the changes?

0 Malik Barton57 over 4 years ago in reply to David Mckinney

TI__Guru 64326 points

Hi David,

Changes over I2C should be observed in "real" time in I2C, no reset needed. When changing DIRSEL bits the biggest observed difference would be source and sink modes. For example one input path changes from DRX to UTX.

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TUSB1044: DIR_SEL