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Software Developer’s Manual 143
Power Management
If power management is not disabled and when the Data_Select field is programmed to 0 or 4, the
Ethernet controller sets the Data Register to the
D0 Power value in the EEPROM. When the
Data_Select field is programmed to 3 or 7, the Ethernet controller sets the Data Register to the D3
Power
value in the EEPROM. Otherwise it returns 0b.
6.4 Wakeup
The Ethernet controller supports two types of wakeup mechanisms:
• Advanced Power Management (APM) Wakeup
• ACPI Power Management Wakeup
Note: The 82541ER contains power management logic, but is not spec-compliant, because it does not
assert PME# for Magic Packets, Network Wakeup Packets, or link change status.
The ACPI Power Management Wakeup uses the PME# pin to wake up the system. The Advanced
Power Management Wakeup uses the PME# pin.
6.4.1 Advanced Power Management Wakeup
“Advanced Power Management Wakeup”, or “APM Wakeup”, was previously known as “Wake on
LAN”. The basic premise is to receive a broadcast or unicast packet with an explicit data pattern,
and then to assert a signal to wake up the system. In the earlier generations of the Ethernet
controller, this was accomplished by using special signal. The Ethernet controller would assert the
signal for approximately 50 ms to signal a wakeup. The
82544GC/EI uses the APM_WAKEUP
pin for this function. For the remaining Ethernet controllers, the PCI PME# signal has been used to
wake up the system.
On power-up, the Ethernet controller reads the
APM Enable bits from the EEPROM Initialization
Control Word 2 into the
APM Enable (APME) bits of the Wakeup Control Register (WUC). These
bits control enabling of APM Wakeup.
When APM Wakeup is enabled, the Ethernet controller checks all incoming packets for “Magic
Packets”. See Section 6.4.3.1.4 for a definition of “Magic Packets*”.
Once the Ethernet controller receives a matching magic packet, it:
• Sets the PME_Status bit in the Power Management Control / Status Register (PMCSR) and
asserts PME#. If the
Assert PME On APM Wakeup (APMPME) bit is set in the Wakeup
Control Register (WUCR).
• Stores the first 128 bytes of the packet in the Wakeup Packet Memory (WUPM).
• Sets the Magic Packet Received bit in the Wakeup Status Register (WUS).
• Sets the packet length in the Wakeup Packet Length Register (WUPL).
• Asserts PME# until the driver clears the Magic Packet Received AMAG bit in the Wakeup
Status Register (WUS), the driver clears the
Assert PME On APM Wakeup (APMPME) bit in
the Wakeup Control Register (WUC), or the driver disables APM Wakeup.
• For the 82544GC/EI only, asserts APM_WAKEUP for 50 ms. For purposes of
APM_WAKEUP assertion, the
82544GC/EI ignores any additional magic packets received
during that 50 ms. If the
82544GC/EI receives another magic packet afterwards, it reasserts
APM_WAKEUP for another 50 ms.