82801BA Datasheet, PDF (78/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Functional Description
5.2.3.4
When the LAN Controller is in one of the low power states, it searches for a predefined pattern in
the first 128 bytes of the incoming packets. The only exception is the Magic Packet, which is
scanned for the entire frame. The LAN Controller will classify the incoming packets as one of the
following categories:
• No Match: The LAN Controller discards the packet and continues to process the incoming
packets.
• Wake-up Packet: The LAN Controller is capable of recognizing and storing the first
128 bytes of a wake-up packet. If a wake-up packet is larger than 128 bytes, its tail is discarded
by the LAN Controller. After the system is fully powered-up, software has the ability to
determine the cause of the wake-up event via the PMDR and dump the stored data to the host
memory.
Magic Packets are an exception. The magic packets may cause a power management event and
set an indication bit in the PMDR; however, it is not stored by the LAN Controller for use by
the system when it is woken up.
Link Status Change Event
The LAN Controller link status indication circuit is capable of issuing a PME on a link status
change from a valid link to an invalid link condition or vice versa. The LAN Controller reports a
PME link status event in all power states. If the WOL bit in the EEPROM is not set, the PME#
signal is gated by the PME Enable bit in the PMCSR and the CSMA Configure command.
Wake on LAN (Preboot Wake-up)
The LAN Controller enters WOL mode after reset if the WOL bit in the EEPROM is set. At this
point, the LAN Controller is in the D0u state.
When the LAN Controller is in WOL mode:
• The LAN Controller scans incoming packets for a Magic Packet and asserts the PME# signal
for 52 ms when a one is detected in Wake on LAN mode.
• The Activity LED changes its functionality to indicates that the received frame passed
Individual Address (IA) filtering or broadcast filtering.
• The PCI Configuration registers are accessible to the host.
The LAN Controller switches from WOL mode to the D0a power state following a setup of the
Memory or I/O Base Address Registers in the PCI configuration space.
5-16
82801BA ICH2 and 82801BAM ICH2-M Datasheet