Intel 82550 Switch User Manual


 
140 10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual
Wake-up Functionality
A.2 Low Power Modes
The device wake-up capabilities require internal PHY and CSMA blocks to be fully active. When
the controller is set into the D2 or D3 power state and wake up is disabled, the internal PHY and
CSMA units are set into low power modes. In this mode, the device loses the link connection. In
D1, the PHY and CSMA units are always active.
Note: Placing the device into low power mode (D2 or D3 power state) with the PME enable bit cleared
immediately turns off the internal PHY unit. Setting the PME enable bit while the controller is in a
low power state will power up the internal PHY and establish link connection. If the wake up on
link status change feature is enabled, the 82558 (or later generation controller) will wake up the
system. To prevent the above scenario, the PME enable bit should be active before the device is set
into low power mode.
A.3 Power Management Context After Reset
The controller has two hardware reset signals that are both active low:
RST#. This is the PCI bus reset, which is active on power up of the PCI power source.
ALTRST#. This is the power on reset (POR) and is active on power up of the auxiliary power
source. It is connected to the system auxiliary power good signal.
The PCI Power Management Specification requires that the PME status and PME enable bits in the
PMCSR will not be cleared by PCI RST# if the function supports wake up from the D3
cold
state. If
the device samples link status (LISTAT) at 0 after a hardware reset, it assumes that an auxiliary
power source is used and wake up from D3
cold
is possible. In this case, assertion of RST# does not
clear these bits.
In order to support Wake on LAN (WOL) mode (preboot wake up), the controller should be able to
generate a wake up event without any software configuration, including PCI power management
configuration. In this scenario, the default configuration of the power management bits should
enable wake up after a hardware reset. The auxiliary power support indication is used to set these
bits after reset.
External
Clock
Circuit
Auxiliary
Power
Fixed Filtering
Wake Up
a
a. If the PME enable bit is set in the D0 state, the device will assert PME# for every wake-up event. It is BIOS
responsibility to disable PME# in D0.
Flexible Filtering
Wake Up
Link Status
Change Wake Up
PME Support
in PMC
No No D1, D2, D3h D1 D1, D2, D3h 01111b
No Yes D1, D2, D3h, D3c D1 D1, D2, D3h, D3c 11111b
Yes No D1, D2, D3h D1,D2,D3h D1, D2, D3h 01111b
Yes Yes D1,D2, D3h, D3c D1, D2, D3h, D3c D1,D2, D3h, D3c 11111b