IP1000A LF
Preliminary Data Sheet
receive frames with the frame patterns in the transmit FIFO. When a matching frame is received (and
also passes the filtering mode set in the Receive-Mode register), a wake event is signaled.
Frame patterns are written to the transmit FIFO in a single “pseudo-packet”. Prior to transferring this
pseudo-packet, the host system should first set the TxReset in the AsicCtrl (to reset the transmit FIFO
pointers and prevent transmission) then prepare a TFD that points to a single data buffer. The buffer
should contain one or more frame patterns placed contiguously. The number of frame patterns is limited
by the transmit FIFO size. The FragLen field in the TFD must exactly equal the sum of the frame pattern
bytes. Also, the host system must set the WordAlign field to ‘x1’ in the TFC0 field of the TFD to prevent
frame word-alignment. Finally, the host system must write the TFD’s address to the TFDListPtr register
to transfer the frame into the transmit FIFO.
The frame patterns in the transmit FIFO specify which bytes in received frames are to be examined.
Each byte in the transmit FIFO specifies a four bit relative offset (from the start of the received frame) in
the most significant nibble and a four bit length indicator in the least significant nibble. Relative offsets
describe the number of bytes of the received frame to skip from the last relevant byte, beginning with
byte 0x00. Relative offsets with a value of 0xF indicate the actual relative offset is larger than 15, and is
specified by the next 8 bit value in the transmit FIFO. Length indicators with a value of 0xF indicate the
actual length indicator is larger than 15, and is specified by the next 8 bit value in the transmit FIFO. If
both the relative offset, and the length indicator are 0xF, the first byte following the relative offset/length
indicator pair is the actual relative offset, and the second following byte is the actual length indicator. A
byte value of 0x00 indicates the end of the pattern for that wake frame. Immediately following the
end-of-pattern is a 4-byte CRC. The calculation used to for the CRC is the same polynomial as the
Ethernet MAC FCS.
An example pseudo-packet (based on the ARP packet example from Appendix A of the “OnNow Network
Device Class Power Management Specification”) which would be loaded into the transmit FIFO of the
IP1000A LF is shown in Figure 2-2.
Figure 2-2 : Example Pseudo Packet
TxFIFO
pseudo
packet
0xc2
0xf3
0x00
0x10
0xf4
0x71
0xd7
0x08
0x19
offset and length
indicator pairs
CRC to match
end of pattern
Table 2-1 deciphers the pseudo packet inFigure 2-2 indicating the relative offset and length indicators
which the IP1000A LF will apply to all receive frames.
17/75
July 5, 2005
Copyright © 2005, IC Plus Corp.
IP1000A LF-DS-R08
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