HP D315 manual Power Control, System State Pressed Power Button Results

Technical Reference Guide

7.2.2 POWER CONTROL

The power supply assembly is controlled digitally by the PS On signal (Figure 7-1). When PS On is asserted, the Power Supply Assembly is activated and all voltage outputs are produced. When PS On is de-asserted, the Power Supply Assembly is off and all voltages (except +5 AUX) are not generated. Note that the +5 AUX voltage is always produced as long as the system is connected to a live AC source.

7.2.2.1 Power Button

The PS On signal is typically controlled through the Power Button which, when pressed and released, applies a negative (grounding) pulse to the power control logic. The resultant action of pressing the power button depends on the state and mode of the system at that time and is described as follows:

System State	Pressed Power Button Results In:
Off	Negative pulse, of which the falling edge results in power control logic asserting PS
	On signal to Power Supply Assembly, which then initializes. ACPI four-second
	counter is not active.
On, ACPI Disabled	Negative pulse, of which the falling edge causes power control logic to de-assert the
	PS On signal. ACPI four-second counter is not active.
On, ACPI Enabled	Pressed and Released Under Four Seconds:
	Negative pulse, of which the falling edge causes power control logic to
	generate SMI-, set a bit in the SMI source register, set a bit for button status,
	and start four-second counter. Software should clear the button status bit
	within four seconds and the Suspend state is entered. If the status bit is
	not cleared by software in four seconds PS On is de-asserted and the
	power supply assembly shuts down (this operation is meant as a guard if
	the OS is hung).
	Pressed and Held At least Four Seconds Before Release:
	If the button is held in for at least four seconds and then released, PS On is
	negated, de-activating the power supply.

Compaq D315 and hp d325 Personal Computers 7-3

Featuring the AMD Athlon XP Processor

Second Edition - April 2003