CME136686LX Hardware Manual - RTD Embedded Technologies ...

Advanced Configuration and Power Interface (ACPI)
The cpuModule supports several different ACPI low power modes, including the S1, S3, S4, and S5 sleeping states.
The BIOS setup utility provides an option to select between S1 and S3 as the Standby state. Sleep modes S4 and
S5 are setup by the operating system.
The cpuModule’s ACPI suspend modes are described below
• S1 (Power on Suspend): The S1 low power state consumes the most power of all supported ACPI sleep
modes. In this mode, the CPU stops executing instructions, but power to the CPU and RAM is
maintained.
• S3 (Suspend to RAM): Everything in the system is powered off except for the system memory. When
the system wakes from this mode, operating systems allow applications to resume where they left off,
as the state of the application is preserved in memory.
• S4 (Hibernate): When the system enters this state, the operating system will save the current state of
applications and relevant data to disk, thus allowing the system RAM to be powered down.
• S5 (Soft-Off): The system is in a soft off state, and must be rebooted when it wakes.
Power Button Modes
The soft power button input of the utility port connector (CN5) can be configured by the operating system as
a suspend button (transition to S1 or S3) or as soft power button (transition to S5). Consult your operating
system documentation for information on how to configure it. The power button will always cause a transition
to S5 if pressed for 4 seconds or longer, without interaction from the operating system.
Low-Power Wake Options
While the soft power button input on the utility power connector (CN5) may be used to enter a low power sleep
state, it may also be used to wake the system.
The reset button input, also on the utility power connector (CN5), may be configured as a power button to wake
this system. This is especially useful in a chasis which has access to the reste button, but the power button is not
accessable. The settings to setup the behavior of the reset button input can be found in the BIOS setup.
80 CME136686LX cpuModule BDM-610000065 Rev C