NH82801HEM S LA5R Intel, NH82801HEM S LA5R Datasheet - Page 210

• Manufacturer Part Number: NH82801HEM S LA5R
• Manufacturer: Intel

Specifications of NH82801HEM S LA5R

• Lead Free Status / RoHS Status: Compliant

5.18.7
Table 84.
5.18.8
Note:
210
USB Power Management
The Host controller can be put into a suspended state and its power can be removed.
This requires that certain bits of information are retained in the resume power plane of
the ICH8 so that a device on a port may wake the system. Such a device may be a fax-
modem, which will wake up the machine to receive a fax or take a voice message. The
settings of the following bits in I/O space will be maintained when the ICH8 enters the
S3, S4, or S5 states.
Bits Maintained in Low Power States
When the ICH8 detects a resume event on any of its ports, it sets the corresponding
USB_STS bit in ACPI space. If USB is enabled as a wake/break event, the system
wakes up and an SCI generated.
USB Legacy Keyboard Operation
When a USB keyboard is plugged into the system, and a standard keyboard is not, the
system may not boot, and MS-DOS legacy software will not run, because the keyboard
will not be identified. The ICH8 implements a series of trapping operations which will
snoop accesses that go to the keyboard controller, and put the expected data from the
USB keyboard into the keyboard controller.
The scheme described below assumes that the keyboard controller (8042 or
equivalent) is on the LPC bus.
This legacy operation is performed through SMM space.
and Status path. The latched SMI source (60R, 60W, 64R, 64W) is available in the
Status Register. Because the enable is after the latch, it is possible to check for other
events that didn't necessarily cause an SMI. It is the software's responsibility to
logically AND the value with the appropriate enable bits.
Note also that the SMI is generated before the PCI cycle completes (e.g., before TRDY#
goes active) to ensure that the processor doesn't complete the cycle before the SMI is
observed. This method is used on MPIIX and has been validated.
The logic also needs to block the accesses to the 8042. If there is an external 8042,
then this is simply accomplished by not activating the 8042 CS. This is simply done by
logically ANDing the four enables (60R, 60W, 64R, 64W) with the 4 types of accesses to
determine if 8042CS should go active. An additional term is required for the “pass-
through” case.
The state table for the diagram is shown in
Port Status and
Command
Register
Control
Status
10h & 12h
Offset
00h
02h
Bit
12
3
2
2
6
8
Enter Global Suspend Mode (EGSM)
Resume Detect
Port Enabled/Disabled
Resume Detect
Low-speed Device Attached
Suspend
Table
85.
Figure 15
Description
Intel
shows the Enable
®
Functional Description
ICH8 Family Datasheet