LAN9500AI datasheet(59/213 Pages) MICROCHIP

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DS00001875A-page 59

LAN950x

5.5.4.4

Inverse Filtering

In inverse filtering, the 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.

5.5.5

WAKEUP FRAME DETECTION

Setting the Wakeup Frame Enable (WUEN) bit in the Wakeup Control and Status Register (WUCSR), places the MAC

in the wakeup frame detection mode. In this mode, normal data reception is disabled, and detection logic within the MAC

examines receive data for the pre-programmed wakeup frame patterns. When a wakeup pattern is received, the Remote

Wakeup Frame Received (WUFR) bit in the WUCSR is set, the device places itself in a fully operational state, and

remote wakeup is issued. The Host will then resume the device and read the WUSCR register to determine the condition

that caused the remote wakeup. Upon determining that the WUFR bit is set, the Host will know a wakeup frame detec-

tion event was the cause. The Host will then clear the WUFR bit, and clear the WUEN bit to resume normal receive

operation. Please refer to Section 7.4.12, "Wakeup Control and Status Register (WUCSR)," on page 172 for additional

information on this register.

Before putting the MAC into the wakeup 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 Wakeup Frame Filter register

(WUFF). Please refer to Section 7.4.11, "Wakeup Frame Filter (WUFF)," on page 171 for additional information on this

The number of programmable wakeup filters supported by the MAC is device dependent. Table 5-46 indicates the num-

ber of wakeup frame filters contained in the WUFF of each LAN950x family device. The number of writes/reads required

to program the WUFF or read its contents, respectively, is also indicated.

The programmable filters support many different receive packet patterns. If remote wakeup mode is enabled, the remote

wakeup function receives all frames addressed to the MAC. It then checks each frame against the enabled filter and

recognizes the frame as a remote wakeup frame if it passes the WUFF’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 supported filters.

The pattern’s offset defines the location of the first byte that should be checked in the frame. The byte mask is a 128-

bit field that specifies whether or not each of the 128 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 Wakeup Frame Filter register, the Host LAN driver software must perform the number of writes indi-

cated in Table 5-46 to the device’s Wakeup Frame Filter register (WUFF). The contents of the Wakeup Frame Filter reg-

ister may be obtained by reading it. The number of reads required to extract the entire contents of the device’s WUFF

is also indicated in Table 5-46.

Table 5-47 shows the wakeup frame filter register’s structure for LAN9500/LAN9500i, while Table 5-48 shows that for

LAN9500A/LAN9500Ai. Component elements common to both register structures follow their definition in this section.

TABLE 5-46:

WAKEUP FRAME FILTER CAPACITY

Device

Number of Filters

Number of Writes/Reads

LAN9500/LAN9500i

420

LAN9500A/LAN9500Ai

840

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