Compaq 850 USB Programming, USB Configuration, USB Control, USB Interface Configuration Registers

Chapter 5 Input/Output Interfaces

5.7.2 USB PROGRAMMING

Programming the USB interface consists of configuration, which typically occurs during POST, and control, which occurs at runtime.

5.7.2.1 USB Configuration

The USB interface operates as a PCI device (31) within the 82801 ICH2 component (functions 2 and 4) and is configured using PCI Configuration Registers as listed in Table 5-17.

Table 5–17. USB Interface Configuration Registers

Table 5-17.

USB Interface Configuration Registers

PCI			PCI
Config.		Reset	Config.		Reset
Addr.	Register	Value	Addr.	Register	Value
00, 01h	Vender ID	8086h	0Eh	Header Type	00h
02, 03h	Device ID	2442h or 2444h	20-23h	I/O Space Base Address	1
04, 05h	PCI Command	0000h	2C, 2Dh	Sub. Vender ID	00h
06, 07h	PCI Status	0280h	3Ch	Interrupt Line	00h
08h	Revision ID	00h	3Dh	Interrupt Pin	03h
09h	Programming I/F	00h	60h	Serial Bus Release No.	10h
0Ah	Sub Class Code	03h	C0, C1h	USB Leg. Kybd./Ms. Cntrl.	2000h
0Bh	Base Class Code	0Ch	C4h	USB Resume Enable	00h

5.7.2.2 USB Control

The USB is controlled through I/O registers as listed in table 5-18.

Table 5–18. USB Control Registers

Table 5-18.

USB Control Registers

I/O Addr.	Register	Default Value
00, 01h	Command	0000h
02, 03h	Status	0000h
04, 05h	Interupt Enable	0000h
06, 07	Frame Number	0000h
08, 0B	Frame List Base Address	0000h
0Ch	Start of Frame Modify	40h
10, 11h	Port 1 Status/Control	0080h
12, 13h	Port 2 Status/Control	0080h
18h	Test Data	00h

5-24Compaq Deskpro EXS and Workstation 300 Personal Computers

Featuring the Intel Pentium 4 Processor

First Edition – December 2000