HD3SS3220: MODE can't be change by MODE_SELECT in attached state

Takahiro Saito

Part Number: HD3SS3220

Hi team,

My customer tried to change MODE by MODE_SELECT register in attached state.

However, the register value is automatically over-write after writing MODE_SELECT register.

Is this the expected operation on HD3SS3220? The reason why the MODE is automatically over-write by IC is that MODE change in attached state is not allowed in USB-C specification, right?

The below procedure is used for changing MODE in attached state. If you find any wrong step, please let me know.

[Procedure] [0x08] [0x09] [0x0a]
1. Power on 0x00 0x20 0x00
2. DISABLE _UFP_ ACCESSORY =1 0x00 0x21 0x00
3. MODE_SELECT=DFP 0x00 0x20 0x20
4. Connect UFP device 0x00 0x71 0x20
5. Clear Interruption 0x00 0x61 0x20
6. MODE_SELECT becomes UFP 0x00 0x31 0x10

Regards,

Saito

over 5 years ago

0 David (ASIC) Liu over 5 years ago

TI__Guru**** 177676 points

Saito-san

The MODE_SELECT can only be changed when in the UNATTACHED state,not in the ATTACHED state.

Thanks

David

0 Takahiro Saito over 5 years ago in reply to David (ASIC) Liu

TI__Expert 5455 points

Hi David,

The register value is automatically over-write after writing MODE_SELECT register when MODE is changed in attached state.

Is that expected operation on HD3SS3220?

Thanks

Saito

0 David (ASIC) Liu over 5 years ago in reply to Takahiro Saito

TI__Guru**** 177676 points

Saito-san

The MODE_SELECT can only be changed when in the UNATTACHED state, the behavior of writing MODE_SELECT when in ATTACHED state is not guaranteed.

Thanks

David

0 Takahiro Saito over 5 years ago in reply to David (ASIC) Liu

TI__Expert 5455 points

Hi David,

The reason why HD3SS3220 doesn't allow to change the mode in attached state is that changing Mode in attached state violates type-c specifiction, is that correct?

Regards,

Saito

0 David (ASIC) Liu over 5 years ago in reply to Takahiro Saito

TI__Guru**** 177676 points

Saito-san

Please refer to chapter 4 of the Type-C spec. The MODE_SELECT defines the HD3SS3220 role in the UNATTACHED state. If mode needs to be changed in the ATTACHED state, you have to use the PD command, DR_SWAP for data role swap, or PR_SWAP for power role swap.

Thanks

David

0 Takahiro Saito over 5 years ago in reply to David (ASIC) Liu

TI__Expert 5455 points

Hi David,

One more question.

When they changed MODE_SELECT register, the value was automatically over-write after writing MODE_SELECT register.

Does HD3SS3220 have such a mechanism intentionally?

Regards,

Saito

0 David (ASIC) Liu over 5 years ago in reply to Takahiro Saito

TI__Guru**** 177676 points

Saito-san

No, if you write to the MODE_SELECT bits, it should stay, and not automatically gets over-written.

But again, why do they want to write to MODE_SELECT in the ATTACHED state, write to MODE_SELECT in ATTACHED state has no effect.

Thanks

David

0 Takahiro Saito over 5 years ago in reply to David (ASIC) Liu

TI__Expert 5455 points

Hi David-san,

Thanks. Customer just mistakenly changed MODE_SELECT register and saw the behavior. They just wonder the reason of the behavior.

They don't use such a control on the actual their products.

Regards,

Saito

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HD3SS3220: MODE can't be change by MODE_SELECT in attached state