Using wake-up frames, Magic packet mode, Network wake-up frame – Maxim Integrated High-Speed Microcontroller Users Guide: Network Microcontroller Supplement User Manual

Page 187: Table 22-4. network wake-up frame patterns

High-Speed Microcontroller User’s

Guide: Network Microcontroller

Supplement

187

USING WAKE-UP FRAMES

As discussed in the DS80C400 data sheet, the Ethernet controller can be placed into a low-power sleep mode such that it can be awak-

ened by a user-programmable network wake-up frame and/or magic packet. The magic packet must conform to a specific predefined

frame format, while the user-programmable network wake-up frame gives the application flexibility in defining the wake-up frame.

MAGIC PACKET MODE

When put into the magic packet mode, the power-management block constantly monitors each frame addressed to the device for a

specific magic packet pattern. Only packets that pass the current destination address filter are checked against the magic packet

requirement. Each frame received is checked for an FFFF_FFFF_FFFFh pattern after the destination and source address fields. This

pattern must be followed by 16 repetitions of the physical MAC address without any breaks or interruptions. In case of a break in the

16 repetitions of the MAC physical address, the FFFF_FFFF_FFFFh pattern is scanned for again in the frame. The 16 repetitions can be

anywhere in the frame, but they must be preceded by the synchronization stream.

For example, if the MAC address of a device were 00-11-22-33-44-55, then the MAC would scan for the following frame data sequence:

[DestinationAddress][ SourceAddress] ................FFFF FFFF FFFF 0011 2233 4455 0011 2233 4455

0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455

0011 2233 4455 0011 2233 4455 ...............CRC

NETWORK WAKE-UP FRAME

Before putting the MAC into sleep mode, the host provides a list of sample frames and the corresponding byte masks to the wake-up

frame filter register in the power-management block through the wake-up frame filter (28h) register. In order to know which bytes of each

receive frame should be included in the CRC-16 calculation, the power-management block uses a programmable byte mask and a pro-

grammable pattern offset for each of the supported filters. In order to load the wake-up frame filter register, the host has to perform

eight writes to the wake-up frame filter register. The wake-up frame filter structure is illustrated in the DS80C400 data sheet. The first

write loads the filter 0 byte mask, the second write loads the filter 1 byte mask and so on. The fifth write loads the filter command nib-

ble for each frame filter. Bit 3 of each filter [0,1,2,3] command nibble, or wake source (WS), is used in conjunction with the global uni-

cast (GU) bit of the wake-up events control and status (2Ch) CSR register to define what type of frames are compared to the wake-up

frame filters. Bit 0 of each filter [0,1,2,3] command nibble enables the associated wake-up frame filter. Table 22-4 summarizes the pos-

sible GU, WS bit combinations. Note that a broadcast frame is always compared versus the enabled wake-up frame filters. One option

to easily allow any broadcast frame to serve as a network wake-up frame is to disable all filter byte mask bits (= 00_00_00_00h) and

designate that the required filter CRC-16 be 0000h (default CRC-16 value). Steps 1 through 8 show an example sequence for pro-

gramming wake-up filter 0. Figure 22-14 shows the resultant filter.

Table 22-4. Network Wake-Up Frame Patterns

GU, WS

NETWORK WAKE-UP FRAME CRITERIA (IF FRAME FILTER ENABLED)

Unicast, pass destination address filter, pass wake-up frame filter

Multicast, pass destination address filter, pass wake-up frame filter

Unicast, pass wake-up frame filter

Multicast, pass wake-up frame filter

Broadcast, pass wake-up frame filter

Maxim Integrated