LAN8742AI-CZ datasheet(42/124 Pages) MICROCHIP

42 / 124 page

LAN8742A/LAN8742Ai

DS00001989A-page 42

 2013-2015 Microchip Technology Inc.

3.8.4.3

Magic Packet Detection

When enabled, the Magic Packet detection mode allows the triggering of the nINT or nPME pin when a Magic Packet

frame is received. A Magic Packet is a frame addressed to the device - either a unicast to the programmed address, or

a broadcast - which contains the pattern 48’h FF_FF_FF_FF_FF_FF after the destination and source address field, fol-

lowed by 16 repetitions of the desired MAC address (loaded into the MAC Receive Address A Register (RX_ADDRA),

MAC Receive Address B Register (RX_ADDRB), and MAC Receive Address C Register (RX_ADDRC)) without any

breaks or interruptions. In case of a break in the 16 address repetitions, the logic scans for the 48’h

FF_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 frame must also pass the FCS check and packet length checking.

As an example, if the desired address is 00h 11h 22h 33h 44h 55h, then the logic 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

…FCS

As an example, the Host system must perform the following steps to enable the device to assert nINT on detection of a

Magic Packet WoL event:

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).

Set the Magic Packet Enable (MPEN) bit of the Wakeup Control and Status Register (WUCSR) to enable Magic

Packet detection.

Set bit 8 (WoL event indicator) in the Interrupt Mask Register to enable WoL events to trigger assertion of the

nINT interrupt pin.

When a match is triggered, the nINT interrupt pin will be asserted, bit 8 of the Interrupt Source Flag Register will be set,

and the Magic Packet Received (MPR) bit of the Wakeup Control and Status Register (WUCSR) will be set.

3.8.4.4

Wakeup Frame Detection

When enabled, the Wakeup Frame detection mode allows the triggering of the nINT or nPME pin when a pre-pro-

grammed Wakeup Frame is received. Wakeup Frame detection provides a way for system designers to detect a cus-

tomized pattern within a packet via a programmable wake-up frame filter. The filter has a 128-bit byte mask that indicates

which bytes of the frame should be compared by the detection logic. A CRC-16 is calculated over these bytes. The result

is then compared with the filter’s respective CRC-16 to determine if a match exists. When a wake-up pattern is received,

the Remote Wakeup Frame Received (WUFR) bit of the Wakeup Control and Status Register (WUCSR) is set.

If enabled, the filter can also include a comparison between the frame’s destination address and the address specified

in the MAC Receive Address A Register (RX_ADDRA), MAC Receive Address B Register (RX_ADDRB), and MAC

Receive Address C Register (RX_ADDRC). The specified address can be a unicast or a multicast. If address matching

is enabled, only the programmed unicast or multicast address will be considered a match. Non-specific multicast

addresses and the broadcast address can be separately enabled. The address matching results are logically OR’d (i.e.,

specific address match result OR any multicast result OR broadcast result).

Whether or not the filter is enabled and whether the destination address is checked is determined by configuring the

Wakeup Filter Configuration Register A (WUF_CFGA). Before enabling the filter, the application program must provide

the detection logic with the sample frame and corresponding byte mask. This information is provided by writing the

Wakeup Filter Configuration Register A (WUF_CFGA), Wakeup Filter Configuration Register B (WUF_CFGB), and

Wakeup Filter Byte Mask Registers (WUF_MASK). The starting offset within the frame and the expected CRC-16 for

the filter is determined by the Filter Pattern Offset and Filter CRC-16 fields, respectively.

If remote wakeup mode is enabled, the remote wakeup function checks each frame against the filter and recognizes the

frame as a remote wakeup frame if it passes the filter’s address filtering and CRC value match.

Note:

Alternatively, the LED1/nINT/nPME or LED2/nINT/nPME pin can be used to indicate a WoL event. Refer

to Section 3.8.4, "Wake on LAN (WoL)" for additional information.

LAN8742Ai-CZ Datasheet(PDF) 42 Page - Microchip Technology

LAN8742Ai-CZ Datasheet(HTML) 42 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL