Multiple Commands in USB-2 - UAS

Curtis Stevens curtis.stevens at
Sat Aug 22 13:22:07 PDT 2009

* From the T10 Reflector (t10 at, posted by:
* "Curtis Stevens" <curtis.stevens at>
	If you have a design which uses a UAS driver communicating with a
USB-2, the USB-2 driver should be ready to receive any type of IU on the
status pipe.  The UAS driver will examine the packet, check the IU type, and
the tag, to determine what happens next.  The initiator port is unable to
pre-determine which IU type will be returned by the device.  In plain terms,
the queued environment enabled by UAS does not allow for the UAS Initiator
port to be expecting any single IU.
Curtis E. Stevens
Sr. Staff  Engr - Standards & Features Technology
20511 Lake Forest Drive #A 113-F
Lake Forest, California 92630
Phone: 949-672-7933
Cell: 949-307-5050
E-Mail: Curtis.Stevens at
-----Original Message-----
From: Madhukar [mailto:madhukar.gubba at] 
Sent: Saturday, August 22, 2009 2:46 AM
To: Curtis Stevens
Cc: t10 at
Subject: Re: Multiple Commands in USB-2 - UAS
On Thu, Aug 20, 2009 at 7:06 PM, Madhukar<madhukar.gubba at> wrote:
> Thank You for the replies.
> I have one last question. If USB2.0 supports multiple command
> processing, here is the scenario where I am getting problem
> If "UAS initiator port" issues a READ command followed by WRITE
> command, the SENSE_IU (of READ command) data buffer is getting filled
> with the data of WRITE_READY issued for WRITE command by the "UAS
> target port" at the HCD level.
> This is happening because when UAS Initiator port is expecting
> SENSE_IU (for READ Command) the UAS target port sent WRITE_READY (for
> WRITE Command) to UAS Initiator port on same pipe.
> I am assuming that the READ and WRITE can be processed simultaneously
> at "UAS target port" and there is no verification of Tag values of
> request and response at HCD level in USB 2.0.
I'm in midway of the implementation. Any help is much appreciated.
Thanks and Regards,
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at

More information about the T10 mailing list