PORTS Forum

Ports and Interfaces => USB => Topic started by: KOTTA on July 01, 2010, 09:49:54 pm

Title: REGARDING THE SET_ADDRESS REQUEST WHEN DEVICE BEING IN ADDRESS STATE
Post by: KOTTA on July 01, 2010, 09:49:54 pm

Hi USB innovators,

Could any body clarify the following

  As per sec:9.46 following statement is there,

Address state:
If the address specified is zero, then the device shall enter the Default state; otherwise, the device remains in the Address state but uses the newly-specified address.

By the above statements can it be like "Two SET_ADDRESS requests can come one after the other" (i.e. once SET_ADDRESS with X address and next SET_ADDRESS with Y address will come ???).

But by ENUMERATION guidelines Sec: 9.1.2 SET_ADDRESS will come once until warm reset was issued.

How to understand the contradiction part about SET_ADDRESS.

Regards,
Sreedhar,

Title: Re: REGARDING THE SET_ADDRESS REQUEST WHEN DEVICE BEING IN ADDRESS STATE
Post by: Ron Hemphill on July 02, 2010, 11:12:23 am

If the device is already in the address state, short of a reset, I don't think I've ever seen or heard of a host issuing another set address to change the address or put it back to default.  I really don't think you need to worry much about this as most USB chips handle the set_address request directly (many don't even give firmware a chance to respond at all), and I suspect most of them will expect a single set_address until reset.

Title: Re: REGARDING THE SET_ADDRESS REQUEST WHEN DEVICE BEING IN ADDRESS STATE
Post by: KOTTA on July 06, 2010, 06:34:14 am

Thanks Ron Hemphill....

Also can u also check my "LFPS" query if you are aware...

Regards,
Sreedhar...