82801DB Datasheet, PDF (407/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

USB UHCI Controllers Registers
11.2 USB I/O Registers
Some of the read/write register bits which deal with changing the state of the USB hub ports
function such that on read back they reflect the current state of the port, and not necessarily the
state of the last write to the register. This allows the software to poll the state of the port and wait
until it is in the proper state before proceeding. A Host controller reset, Global reset, or Port reset
will immediately terminate a transfer on the affected ports and disable the port. This affects the
USBCMD register, bit [4] and the PORTSC registers, bits [12, 6, 2]. See individual bit descriptions
for more detail.
Table 11-2. USB I/O Registers
Offset
00–01h
02–03h
04–05h
06–07h
08–0Bh
0Ch
0D–0Fh
Mnemonic
Register
USBCMD USB Command
USBSTS USB Status
USBINTR USB Interrupt Enable
FRNUM
USB Frame Number
FRBASEADD USB Frame List Base Address
SOFMOD
USB Start of Frame Modify
Reserved
10–11h
PORTSC0 Port 0 Status/Control
12–13h
14–17h
PORTSC1
Port 1 Status/Control
Reserved
Default
0000h
0020h
0000h
0000h
Undefined
40h
0
0080h
0080h
0
Type
R/W
R/WC
R/W
R/W ⁽¹⁾
R/W
R/W
RO
R/WC, R/W,
RO ⁽¹⁾
R/WC, R/W,
RO ⁽¹⁾
RO
NOTES:
1. These registers are Word writable only. Byte writes to these registers have unpredictable effects.
Intel^® 82801DB ICH4 Datasheet
407