AT43USB325 datasheet(81/109 Pages) ATMEL

81 / 109 page

3355C–USB–4/05

AT43USB325

8.4

USB Hub

The hub in a USB system provides for the electrical interface between USB devices and the

host. The major functions that the hub must supports are:

• Connectivity

• Power management

• Device connect and disconnect

• Bus fault detection and recovery

• Full speed and low speed device support

A hub consists of two major components: a hub repeater and a hub controller. The hub repeater

is responsible for:

• Providing upstream connectivity between the selected device and the Host

• Managing connectivity setup and tear-down

• Handling bus fault detection and recovery

• Detecting connect/disconnect on each port

The Hub Controller is responsible for:

• Hub enumeration

• Providing configuration information to the host

• Providing status of each port to the host

• Controlling each port per host command

The first two tasks of the hub are similar to that of a USB function and are described in detail in

the following section. The descriptions will cover the features of the AT43USB325's hub and how

to program it to make a USB-compliant hub.

Control transactions for the hub control endpoint proceed exactly the same way as those

described for the embedded function. The operation of the hub's endpoint 1 is fully implemented

in the hardware and does not need any firmware support. Any status changes within the hub will

automatically update hub endpoint 1, which will be sent to the host at the next IN token that is

addressed to it. If no change has occurred, the interrupt endpoint will respond with a NAK.

AT43USB325 Datasheet(PDF) 81 Page - ATMEL Corporation