LAN9500AI datasheet(63/213 Pages) MICROCHIP

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DS00001875A-page 63

LAN950x

Note 5-24

As determined by bits 3:2 of Filter i Command.

Note 5-25

When wakeup frame detection is enabled via the Wakeup Frame Enable (WUEN) bit of the Wakeup

Control and Status Register (WUCSR), a broadcast wakeup frame will wake up the device despite

the state of the Disable Broadcast Frames (BCAST) bit in the MAC Control Register (MAC_CR).

5.5.6

MAGIC PACKET DETECTION

Setting the Magic Packet Enable (MPEN) bit in the Wakeup Control and Status Register (WUCSR), places the MAC in

the “Magic Packet” detection mode. In this mode, normal data reception is disabled, and detection logic within the MAC

examines receive data for a Magic Packet. When a Magic Packet is received, the Magic Packet Received (MPR) 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 MPR bit is set, the Host will know reception of a Magic Packet was the cause. The Host will then

clear the MPR bit, and clear the MPEN 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.

In Magic Packet mode, the Power Management Logic constantly monitors each frame addressed to the node for a spe-

cific Magic Packet pattern. It checks only packets with the MAC’s address or a broadcast address to meet the Magic

Packet requirement. The Power Management Logic checks each received frame for the pattern 48h

FF_FF_FF_FF_FF_FF after the destination and source address field.

Then the Function looks in the frame for 16 repetitions of the MAC address without any breaks or interruptions. In case

of a break in the 16 address repetitions, the PMT Function scans for the 48'hFF_FF_FF_FF_FF_FF pattern again in the

incoming frame.

The 16 repetitions may be anywhere in the frame but must be preceded by the synchronization stream. The device will

also accept a multicast frame, as long as it detects the 16 duplications of the MAC address. If the MAC address of a

node is 00h 11h 22h 33h 44h 55h, then the MAC scans for the following data sequence in an Ethernet: Frame.

Destination Address Source Address ……………FF FF FF FF FF FF

00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55

…CRC

5.5.7

RECEIVE CHECKSUM OFFLOAD ENGINE (RXCOE)

The receive checksum offload engine provides assistance to the Host by calculating a 16-bit checksum for a received

Ethernet frame. The RXCOE readily supports the following IEEE802.3 frame formats:

• Type II Ethernet frames

• SNAP encapsulated frames

• Support for up to 2, 802.1q VLAN tags

The resulting checksum value can also be modified by software to support other frame formats.

The RXCOE has two modes of operation. In mode 0, the RXCOE calculates the checksum between the first 14 bytes

of the Ethernet frame and the FCS. This is illustrated in Figure 5-10.

Note:

x indicates “don’t care”.

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