4-Port USB2.0 Controller
Datasheet
SMSC USB20H04
Page 31
Revision 1.63 (10-14-04)
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
12h
01h
0200h
09h
00h
00h
40h
user
user
user
00h
00h
00h
01h
HIGH
SPEED
12h
01h
0200h
09h
00h
01h*
40h
user
user
user
00h
00h
00h
01h
FIELD NAME
DESCRIPTION
0
1
bLength
bDescriptorType
bcdUSB
bDeviceClass
bDeviceSubClass
bDeviceProtcol
bMaxPacketSize0
idVendor
idProduct
bcdDevice
iManufacturer
iProduct
iSerialNumber
iNumConfigurations
Size of this descriptor in bytes
DEVICE Descriptor Type
USB Specification Number
Class code assigned by USB-IF for Hubs
Class code assigned by USB-IF for Hubs
Protocol code assigned by the USB-IF
64-byte packet size
Vendor ID; OEM value
Product ID; OEM value
Device ID; OEM value
This optional string is not supported.
This optional string is not supported.
This optional string is not supported.
Supports 1 configuration
2,3
4
5
6
7
8,9
10,11
12,13
14
15
16
17
* 02h for multiple-TT
Table 9.2 - Device Qualifier Descriptor
OFFSET
FULL
SPEED
0Ah
HIGH
SPEED
0Ah
FIELD NAME
DESCRIPTION
0
bLength
bDescriptorType
bcdUSB
bcdUSB
bDeviceClass
bDeviceSubClass
Size of this descriptor in bytes
1
2
3
4
5
06h
00h
02h
09h
00h
06h
00h
02h
09h
00h
DEVICE Qualifier Type
USB Specification Version Number (LSB)
USB Specification Version Number (MSB)
Class code assigned by USB-IF for Hubs
Class code assigned by USB-IF for Hubs
Protocol code.
64-byte packet size for other speed
6
00h
01h*
bDeviceProtcol
7
8
40h
01h
40h
01h
bMaxPacketSize0
bNumConfigurations
Supports 1 other speed configuration
9
00h
00h
bReserved
Reserved
* 02h for multiple-TT