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
