LAN89218 datasheet(22/148 Pages) MICROCHIP

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LAN89218

DS60001255B-page 22

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3.5

Wake-up Frame Detection

Setting the Wake-up Frame Enable bit (WUEN) in the WUCSR—Wake-up Control and Status Register, places the

LAN89218 MAC in the wake-up frame detection mode. In this mode, normal data reception is disabled, and detection

logic within the MAC examines receive data for the pre-programmed wake-up frame patterns. The LAN89218 can

be programmed to notify the host of the wake-up frame detection with the assertion of the host interrupt (IRQ) or

assertion of the power management event signal (PME). Upon detection, the Wake-Up Frame Received bit (WUFR)

in the WUCSR is set. When the host clears the WUEN bit the LAN89218 will resume normal receive operation.

Before putting the MAC into the wake-up frame detection state, the host must provide the detection logic with a list

of sample frames and their corresponding byte masks. This information is written into the Wake-up Frame Filter

The MAC supports four programmable filters that support many different receive packet patterns. If remote wake-up

mode is enabled, the remote wake-up function receives all frames addressed to the MAC. It then checks each frame

against the enabled filter and recognizes the frame as a remote wake-up frame if it passes the wakeup frame filter

In order to determine which bytes of the frames should be checked by the CRC module, the MAC uses a

programmable byte mask and a programmable pattern offset for each of the four supported filters.

The pattern’s offset defines the location of the first byte that should be checked in the frame. Since the destination

address is checked by the address filtering function, the pattern offset is always greater than 12.

The byte mask is a 31-bit field that specifies whether or not each of the 31 contiguous bytes within the frame,

beginning in the pattern offset, should be checked. If bit j in the byte mask is set, the detection logic checks byte

offset +j in the frame. In order to load the Wake-up Frame Filter register, the host LAN driver software must perform

eight writes to the Wake-up Frame Filter register (WUFF). Table 3-2 shows the wake-up frame filter register’s

structure.

The Filter i Byte Mask defines which incoming frame bytes Filter i will examine to determine whether or not this is a

wake-up frame.

Note:

Wake-up frame detection can be performed when the LAN89218 is in the D0 or D1 power states. In the D0

state, wake-up frame detection is enabled when the WUEN bit is set.

Note:

Wake-up frame detection, as well as Magic Packet detection, is always enabled and cannot be disabled

when the device enters the D1 state.

Note:

When wake-up frame detection is enabled via the WUEN bit of the WUCSR—Wake-up Control and Status

Frame (BCAST) bit in the MAC_CR—MAC Control Register.

TABLE 3-2:

WAKE-UP FRAME FILTER REGISTER STRUCTURE

Filter 0 Byte Mask

Filter 1 Byte Mask

Filter 2 Byte Mask

Filter 3 Byte Mask

Reserved

Filter 3

Command

Reserved

Filter 2

Command

Reserved

Filter 1

Command

Reserved

Filter 0

Command

Filter 3 Offset

Filter 2 Offset

Filter 1Offset

Filter 0 Offset

Filter 1 CRC-16

Filter 0 CRC-16

Filter 3 CRC-16

Filter 2 CRC-16

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