BMC Functional Specifications ESB2 BMC Core TPS
Revision 1.0
Intel order number E18291-001
254
When the system transitions to the off state (S5), the BMC de-asserts the
POWER_ON_ENABLE signal, blocking system power-on.
The BMC monitors the POWER_ON signal (SleepS5) to detect if the chipset is attempting to
power on the system. If so, the BMC completes necessary transitional operations before
asserting POWER_ON_ENABLE and allowing the system power-on to complete.
The BMC also uses the POWER_ON_ENABLE signal to enforce a minimum off-time whenever
the system is shut down. This is currently set to 10 seconds.
Assertion of the FORCE_UPDATE jumper signal allows power on to occur. This handles the
case in which the BMC operational code is not functional.
22.1.5.4 Power-down Disable
The BMC asserts POWER_DOWN_DISABLE to momentarily block system power-down while
transitional operations are completed before allowing the system power-down to complete.
22.1.6 Power State Retention
The BMC persistently stores the latest power state that was attained do to a power state change
initiator. This capability supports the power state restoration feature.
22.1.7 Power State Restoration
The BMC provides the ability to control the AC power-on behavior of the server. The Set Power
Restore Policy command configures the BMC to restore the power state in one of three ways.
Power always off – Leave power off when AC is restored.
Power always on – Power server on when AC is restored.
Restore power state – Restore power state to the state it was in when AC was lost.
When standby power returns after an AC power loss, the BMC activates the server power as
directed by the configuration.
22.1.8 Wake-On-LAN (WOL)
The BMC does not directly participate in WOL. The NICs directly interact with the chipset to
initiate the power on of the system. The BMC blocks power-on until it is ready for the power-on
to occur. See section 22.1.5.3. The BMC must detect when the system is trying to power on and
assert the POWER_ON_ENABLE signal for a WOL-initiated DC power-on to occur.
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