LAN8740A Datasheet, PDF (43/136 Pages) Microchip Technology – Small Footprint MII/RMII 10/100 Energy Efficient Ethernet Transceiver with HP Auto-MDIX and flexPWR® Technology

LAN8740A/LAN8740Ai
As an example, the Host system must perform the following steps to enable the device to assert nINT on detection of a
Wakeup Frame WoL event:
Declare Pattern:
1. Update the Wakeup Filter Byte Mask Registers (WUF_MASK) to indicate the valid bytes to match.
2. Calculate the CRC-16 value of valid bytes off-line and update the Wakeup Filter Configuration Register B
(WUF_CFGB). CRC-16 is calculated as follows:
At the start of a frame, CRC-16 is initialized with the value FFFFh. CRC-16 is updated when the pattern offset and mask
indicate the received byte is part of the checksum calculation. The following algorithm is used to update the CRC-16 at
that time:
Let:
^ denote the exclusive or operator.
Data [7:0] be the received data byte to be included in the checksum.
CRC[15:0] contain the calculated CRC-16 checksum.
F0 … F7 be intermediate results, calculated when a data byte is determined to be part of the CRC-16.
Calculate:
F0 = CRC[15] ^ Data[0]
F1 = CRC[14] ^ F0 ^ Data[1]
F2 = CRC[13] ^ F1 ^ Data[2]
F3 = CRC[12] ^ F2 ^ Data[3]
F4 = CRC[11] ^ F3 ^ Data[4]
F5 = CRC[10] ^ F4 ^ Data[5]
F6 = CRC[09] ^ F5 ^ Data[6]
F7 = CRC[08] ^ F6 ^ Data[7]
The CRC-32 is updated as follows:
CRC[15] = CRC[7] ^ F7
CRC[14] = CRC[6]
CRC[13] = CRC[5]
CRC[12] = CRC[4]
CRC[11] = CRC[3]
CRC[10] = CRC[2]
CRC[9] = CRC[1] ^ F0
CRC[8] = CRC[0] ^ F1
CRC[7] = F0 ^ F2
CRC[6] = F1 ^ F3
CRC[5] = F2 ^ F4
CRC[4] = F3 ^ F5
CRC[3] = F4 ^ F6
CRC[2] = F5 ^ F7
CRC[1] = F6
CRC[0] = F7
3. Determine the offset pattern with offset 0 being the first byte of the destination address. Update the offset in the
Filter Pattern Offset field of the Wakeup Filter Configuration Register A (WUF_CFGA).
Determine Address Matching Conditions:
4. Determine the address matching scheme based on Table 3-8 and update the Filter Broadcast Enable, Filter Any
Multicast Enable, and Address Match Enable bits of the Wakeup Filter Configuration Register A (WUF_CFGA)
accordingly.
5. If necessary (see step 4), set the desired MAC address to cause the wake event in the MAC Receive Address A
Register (RX_ADDRA), MAC Receive Address B Register (RX_ADDRB), and MAC Receive Address C Register
(RX_ADDRC).
6. Set the Filter Enable bit of the Wakeup Filter Configuration Register A (WUF_CFGA) to enable the filter.
 2013-2015 Microchip Technology Inc.
DS00001987A-page 43