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Chapter 5 Input/Output Interfaces
5-24 Compaq Deskpro EXS and Workstation 300 Personal Computers
Featuring the Intel Pentium 4 Processor
First Edition – December 2000
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
Config.
Addr. Register
Reset
Value
PCI
Config.
Addr. Register
Reset
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