USB 3.0's ITP and BIAM

[ChongHan]

Hi all

Good day.

I have some questions about the Isochronous Timestamp Packet (ITP) and Bus Interval Adjustment Message (BIAM):

1) As we know, in USB 3.0, there is a new packet which is ITP, is used to carry host's timing information to devices for synchronization. So, actually what is the "Host's timing information" mean? Is that mean the host' s clock or the external clock from host?

2) I read from the BIAM section in USB 3.0 spec, it stated that BIAM can used by device to synchronize the host's bus interval clock with an external clock. So now, if ITP carry the host's timing info, the device will synchronize to host's clock or external clock?

Sorry for my bad English, hope you all understand my questions and give me a hand. Thanks in advance!

Regards
ChongHan

[Jan Axelson]

1. 8.7 in the USB 3.1 spec says the ITP is based on the microframe interval counter.

2. 8.5.6.6 in the USB 3.1 spec says that the Bus Interval Adjustment Message will be deprecated in a future release so perhaps it's best to not implement it.

[ChongHan]

Hi Sir Jan Axelson

Thank you for your reply. A bit confusing about the specification. Do you know about the reason why the will deprecate this BIAM?
Is that all the function that included (explained) in USB3.0 spec sure can be implemented and work in real application?
For ignoring the future release, is that this function actually working (as stated in USB3.0 spec)?

From the USB 3.1 spec, "The Bus Interval Adjustment Message may be sent only by devices operating at Gen 1 speed and shall be ignored by hosts that are not operating at Gen 1 speed." Is it mean that the BIAM won't work from USB 3.1 and above? Or USB 3.1 still can use it? GEN 1 speed = USB 3.0?

Really thanks for your advices, hope will get more info from you Sir.

Best Regards
ChongHan

[Jan Axelson]

Do you know about the reason why the will deprecate this BIAM?

no

Is that all the function that included (explained) in USB3.0 spec sure can be implemented and work in real application?
For ignoring the future release, is that this function actually working (as stated in USB3.0 spec)?

I don't know.

From the USB 3.1 spec, "The Bus Interval Adjustment Message may be sent only by devices operating at Gen 1 speed and shall be ignored by hosts that are not operating at Gen 1 speed." Is it mean that the BIAM won't work from USB 3.1 and above? Or USB 3.1 still can use it? GEN 1 speed = USB 3.0?

GEN1 = 5 Gbps, GEN2 = 10 Gbps