Mobile Intel
®
945GM Express Chipset
Development Kit User’s Manual 35
Theory of Operation
3.6.1 Transition to S3
If enabled, the transition to S3 from the full-on state can be accomplished in the following ways:
• The OS performs the transition through software.
• Press the front panel power button for less than four seconds (assuming the OS power
management support has been enabled).
Note: The power button is accessed by adding a switch to the pins 5 and 6 on the front panel header J8J1.
3.6.2 Transition to S4
“Wake on S4” (Suspend to disk) is controlled by the operating system.
3.6.3 Transition to S5
The transition to S5 is accomplished by the following means:
• Press the front panel power button for less than four seconds (if enabled through the OS).
• Press the front panel power button for more than four seconds to activate power button
override.
3.6.4 Transition to Full-On
The transition to the Full-On state can be from S3 or S5. The transition from S3 is a low latency
transition that is triggered by one of the following wake events:
• Power management timer expiration
• Real Time Clock (RTC) triggered alarm
• Power button activation
• USB device interrupt
• ICH7M pin PME# assertion
• AC power loss
For AC power loss, the system operation is defined by register settings in the Intel ICH7-M. Upon
the return of power, a BIOS option, set prior to the power loss, allows the system to either go
immediately to the S5 state, or reboot to the Full-On state, no matter what the state was before the
power loss. External logic for this functionality is not necessary. If the BIOS remains in the S5 state
after AC power loss, only the power button or the RTC alarm can bring the system out of the S5
state. The status of enabled wake events will be lost.
3.7 Power Measurement Support
Power measurement resistors are provided on the platform to measure the power of most
subsystems. All power measurement resistors have a tolerance of 1%. The value of these power
measurement resistors are 2 mΩ by default. Power on a particular subsystem is calculated using the
following formula:
To Next Page
Loading...
Need help?
General
