SMSC USB20H04 Chapter 9 Hub Descriptors

4-Port USB 2.0 Hub Controller

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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	HIGH		FIELD NAME	DESCRIPTION
	SPEED	SPEED
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	HIGH		FIELD NAME	DESCRIPTION
	SPEED	SPEED
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
6	00h	01h*		bDeviceProtcol	Protocol code.
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

Revision 1.63 (03-30-07) Page 28 SMSC USB20H04

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