4-Port USB 2.0 Hub Controller

Datasheet

Revision 1.63 (03-30-07)

Page 28

SMSC USB20H04

DATASHEET

Chapter 9

Hub Descriptors

The USB20H04 will not electrically attach to the USB until after it has loaded valid data for all user-defined

descriptor fields. A default configuration is present immediately after RESET_N negation. User defined

configuration values can be loaded from either an external microcontroller or an external EEPROM.

A hub returns different descriptors based on whether it is operating at high-speed or full-/low-speed. A hub

can report three different sets of the descriptors: one descriptor set for full-/low-speed operation and two

sets for high-speed operation. The descriptors reported by the USB20H04 are summarized in the following

tables. The host retrieves this information by using the GetDescriptor request with the corresponding

descriptor type values.

Table 9.1 - Device Descriptor

OFFSET

FULL

SPEED

HIGH

SPEED

FIELD NAME

DESCRIPTION

0

12h

12h

bLength

Size of this descriptor in bytes

1

01h

01h

bDescriptorType

DEVICE Descriptor Type

2,3

0200h

0200h

bcdUSB

USB Specification Number

4

09h

09h

bDeviceClass

Class code assigned by USB-IF for Hubs

5

00h

00h

bDeviceSubClass

Class code assigned by USB-IF for Hubs

6

00h

01h*

bDeviceProtcol

Protocol code assigned by the USB-IF

7

40h

40h

bMaxPacketSize0

64-byte packet size

8,9

user

user

idVendor

Vendor ID; OEM value

10,11

user

user

idProduct

Product ID; OEM value

12,13

user

user

bcdDevice

Device ID; OEM value

14

00h

00h

iManufacturer

This optional string is not supported.

15

00h

00h

iProduct

This optional string is not supported.

16

00h

00h

iSerialNumber

This optional string is not supported.

17

01h

01h

iNumConfigurations

Supports 1 configuration

* 02h for multiple-TT

Table 9.2 - Device Qualifier Descriptor

OFFSET

FULL

SPEED

HIGH

SPEED

FIELD NAME

DESCRIPTION

0

0Ah

0Ah

bLength

Size of this descriptor in bytes

1

06h

06h

bDescriptorType

DEVICE Qualifier Type

2

00h

00h

bcdUSB

USB Specification Version Number (LSB)

3

02h

02h

bcdUSB

USB Specification Version Number (MSB)

4

09h

09h

bDeviceClass

Class code assigned by USB-IF for Hubs

5

00h

00h

bDeviceSubClass

Class code assigned by USB-IF for Hubs

Protocol code.

6

00h

01h*

bDeviceProtcol

7

40h

40h

bMaxPacketSize0

64-byte packet size for other speed

8

01h

01h

bNumConfigurations

Supports 1 other speed configuration

9

00h

00h

bReserved

Reserved

* 02h for multiple-TT