20H04 Datasheet, PDF (31/38 Pages) SMSC Corporation – 4-PORT USB2.0 HUB CONTROLLER

4-Port USB2.0 Controller
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
0
1
2,3
4
5
6
7
8,9
10,11
12,13
FULL
SPEED
12h
01h
0200h
09h
00h
00h
40h
user
user
user
HIGH
SPEED
12h
01h
0200h
09h
00h
01h*
40h
user
user
user
14
00h
00h
15
00h
00h
16
00h
00h
17
01h
01h
* 02h for multiple-TT
FIELD NAME
DESCRIPTION
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
Table 9.2 - Device Qualifier Descriptor
OFFSET
0
1
2
3
4
5
FULL
SPEED
0Ah
06h
00h
02h
09h
00h
6
00h
HIGH
SPEED
0Ah
06h
00h
02h
09h
00h
01h*
FIELD NAME
bLength
bDescriptorType
bcdUSB
bcdUSB
bDeviceClass
bDeviceSubClass
bDeviceProtcol
DESCRIPTION
Size of this descriptor in bytes
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.
7
40h
40h
8
01h
01h
9
00h
00h
* 02h for multiple-TT
bMaxPacketSize0 64-byte packet size for other speed
bNumConfigurations Supports 1 other speed configuration
bReserved
Reserved
SMSC USB20H04
Page 31
DATASHEET
Revision 1.63 (10-14-04)