LAN9115 datasheet(21/114 Pages) MICROCHIP

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DS00002269A-page 21

LAN9115

3.4.2.2

Inverse Filtering

In inverse filtering, the LAN9115 Packet Filter Block accepts incoming frames with a destination address not matching

the perfect address (i.e., the value programmed into the MAC Address High register and the MAC Address Low register

in the CRC block and rejects frames with destination addresses matching the perfect address.

For all filtering modes, when MCPAS is set, all multicast frames are accepted. When the PRMS bit is set, all frames are

accepted regardless of their destination address. This includes all broadcast frames as well.

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

LAN9115 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 LAN9115 can be pro-

grammed 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 LAN9115 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 register

(WUFF). Please refer to Section 5.4.11, "WUFF—Wake-up Frame Filter," on page 87 for additional information on this

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 reg-

ister’s address filtering and CRC value match.

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). The Diagram shown in Table 3-2, "Wake-Up Frame Filter Register Structure"

below, shows the wake-up frame filter register’s structure.

Note 3-1

Wake-up frame detection can be performed when LAN9115 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 3-2

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 3-3

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

Status Register, a broadcast wake-up frame will wake-up the device despite the state of the Disable

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

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. Table 3-3, describes the byte mask’s bit fields.

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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