SB82371 Intel Corporation, SB82371 Datasheet - Page 85

• Manufacturer Part Number: SB82371
• Description: 82371FB (PIIX) AND 82371SB (PIIX3) PCI ISA IDE XCELERATOR
• Manufacturer: Intel Corporation

take effect from the beginning of the next frame. This register is reset upon a Host Controller Reset or Global
Reset. Software must maintain a copy of its value for reprogramming if necessary.
2.8.7.
I/O Address:
Default:
Access:
Size:
After a Power-up and after a RESET, the initial conditions of a port are: No device connected, Port disabled,
and the bus line status is 00 (single-ended zero). Note: If a device is attached, the port state will transition to
the attached state and system software will process this as with any status change notification. It may take
up to 64 USB bit times for the port transition to occur. Note that, if the Host Controller is in Global Suspend
mode, then, if any of bits [6,3,1] gets set, the Host Controller will signal a resume. Refer to Chapter 11 of the
USB Specification for details on hub operation.
7
6:0
Bit
PORTSC Port Status and Control Register
Reserved.
SOF Timing Value. Guidelines for the modification of frame time are contained in Chapter 7 of
the USB Specification. The SOF counter is initialized to a count of 11936. The SOF cycle time
(number of SOF counter clock periods to generate a SOF) is equal to 11936 + value in this
field. The default value is decimal 64 which gives a SOF count value of 12000. For a 12 MHz
SOF counter clock input, this produces a 1 ms Frame period. The following table indicates
what SOF Timing Value to program into this field for a certain frame.
(# 12Mhz Clocks)
Frame Length
(decimal)
11936
11937
11999
12000
12001
12062
12063
Base + (10 11h) Port 1
Base + (12 13h)
0000h
Read/Write (WORD writeable only)
16 bits
.
.
.
.
Port 2
SOF Reg. Value
Description
(decimal)
126
127
63
64
65
0
1
.
.
.
.
82371FB (PIIX) AND 82371SB (PIIX3)
85