Filter
Top Products
Technical Reference Guide
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition - September 1997
7-3
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 (high), the Power Supply Assembly is activated. When PS On is de-asserted, the
Power Supply Assembly (and the rest of the system) is off. The PS On signal is typically
controlled through the Power Button, which can be set by software (Windows 95) to operate as
either a standard On/Off button or as a Suspend button. The resultant action of pressing the
power button depends on the programmed state of the power button.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. Four-second
counter is not active.
On,
Advd. Power Disabled
Negative pulse, of which the rising edge causes power control logic to de-assert
the PS On signal. Four-second counter is not active.
On,
Advd. Power 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 condition is meant as a guard in
case 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.
The PS On signal can also be activated with a power “wake-up” of the system due to the
following events:
Magic Packet - If the network interface controller is enabled for remote wake-up, reception of a
“Magic Packet” results in the NIC component asserting the PINTA- signal to the power control
logic, which in turn asserts the PS On signal and turns on the power supply assembly.
RTC Alarm/Modem Ring - These events (within the 87307 I/O controller) are programmable for
power wake-up and can affect the assertion of the PS On signal through the power control logic.
NOTE:
The PS On signal can be configured to be asserted whenever the power supply
assembly is connected to live AC by setting DIP SW1 position 6 to the “On” (closed or
grounding) position. This condition overrides all other settings.
The power LED is normally on in a steady state with the system on. When the system is in a low
power (suspend) condition the power LED is pulsed, causing it to blink at approximately a rate of
1-Hz. The blinking is affected through the power control logic
The power button can be inhibited by invoking BIOS call INT 15, AX=E828h, which is
discussed in Chapter 8, “BIOS ROM.”