Hi,

I am currently involved with usb 2.0 design. I am a bit confused about address decoding in usb2.0 for the following scenario.

In USB2.0, initially during the control transfer, how do you find whether the packet is addressed to you or not when other USB devices are also connected, say when the system/host is turned on.

Thank You,

Regards,
Harish

you should respond to any packet sent to you when you have the default address before you receive the packet set_address.

all pachets are initiated by the host so you have no collision problem.

usb have 4 pins (D+/- and power pin 5v and GND)

so when you have 5v means the host is turned on.

look you can not communicate directly with the host you should use UTMI interface.
so look to this document:

USB 2.0
Transceiver Macrocell Interface
(UTMI)
Specification
Version 1.05
3/29/2001

good luck

walid aydi

Thank you for replying.

As you had mentioned that device needs to respond to any packet when it has the default address, so if there is any packet on the usb bus with other devices of default address, then who should respond to the packet. Also when host sends "set address" who should accept that packet. Pls help me with this.

Thank You,

Warm Regards,
Harish

The host will only enable one hub port at a time.