Chapter 6 Power and Signal Distribution
Compaq Deskpro EP Series of Personal Computer
First Edition - April 1998
6-4
6.2.2.3 Power Restore Feature
The system includes a power restore feature. A circuit powered by the RTC/CMOS battery holds
the state of the PS On signal so that if a power outage occurs the system, when power is regained,
will revert to the power state of the system at the time power was lost. The power restore feature
can be overridden by two functions:
♦ System On After AC Restore – The system can be configured to come on (after power
restoration) by placing DIP switch SW1-1 to “On” (closed). When enabled the system will
power up every time AC power is reapplied, regardless of the previous “AC applied” state.
♦ System Off After AC Restore – The system can be programmed by software/firmware to
always stay off (after power restoration) through GPO #29. When enabled the system will
stay off every time AC power is reapplied, regardless of the previous “AC applied” state.
6.2.2.4 Wake Up Events
The PS On signal can also be activated with a power “wake-up” of the system due to the
occurrence of a magic packet, serial port ring, or PCI power management (PME) event. These
events can be individually enabled by software through the GPIO of the south bridge to wake up
the system from a sleep (low power) state. The wake up sequence for each event occurs as
follows:
♦ Wake On LAN (WOL) - If a compliant network interface controller is installed and enabled
for remote wake-up, detection of a WOL event results in the assertion of the high R-MPKT
pulse signal (received through the WOL header P9) to the power control logic, which will
assert PS On. Note that the NIC adapter must be able to draw five volts power from header
P9 during the system sleep state. This function is enabled through GPO #28.
♦ Modem Ring – A ring indication on serial port A (COM1) will, if enabled, be detected by the
power control logic and cause the PS On signal to be asserted. This function is enabled
through GPO #27.
♦ PME Event – A power management event that asserts the PME- signal on the PCI bus can
be enabled to cause the power control logic to generate the PS On signal. Note that the PCI
card must have a second source of power to operate during the system unit’s sleep state. This
function is enabled through GPO #26.
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