User guide

PH440 NLX Motherboard User Guide September 1998
MITSUBISHI ELECTRIC MOTHERBOARD DIVISION PAGE 25 OF 51
MOTHERBOARD POWER
Processor Power
A voltage regulator conforming to the Intel VRM8.2 standard supplies power for the processor
core. The motherboard automatically selects the correct processor voltage.
Battery
An IEC-type CR2032 3V lithium coin cell and holder are fitted to the board. Note that when the
motherboard is powered off but the AC remains connected (the standby rail is active) the battery
is not used.
POWER MANAGEMENT
Standby Switch
The motherboard supports an ACPI-compliant standby switch for use with a soft-switch power
supply. The action of the switch is under a combination of hardware and software control and is
summarised in the table below. The motherboard will power off regardless of the state of
software if the switch is held down for more than 4 seconds.
State Action after switch pressed
Standby (soft power off) Machine powers up and executes POST
POST, DOS or APM O/S Machine powers off into standby state
Behaviour After AC-Disconnect
The ‘Wake on AC connect’ BIOS option and the state of the lithium cell determine the
behaviour of the motherboard after an AC-disconnect. The table below describes this.
Conditions Action on AC Reconnect
CMOS RAM cleared. This is the state of a
new motherboard before assembly. This also
occurs after battery removal or failure.
Motherboard waits for standby switch
to be pressed.
CMOS RAM not cleared and ‘Wake on AC
connect’ was set to ‘Enabled’.
Motherboard fully powers up without
intervention.
CMOS RAM not cleared and ‘Wake on AC
connect’ was set to ‘Disabled’. This is the
default state. Resume events will be lost if an
AC power failure occurs.
Motherboard waits for standby switch
to be pressed.
Sleep State Indication
Indication of system activity states is provided by the signal ‘STANDBY_LED#’ to the NLX
riser (pin B159). If this signal is asserted (low) then the system is in a power-managed state. The
implementation of coloured LEDs to indicate system power states is dependent on the NLX riser
used.