Wake on LAN Mode/Low-Power
BCM5718 Programmer’s Guide
Broadcom
®
January 29, 2016 • 5718-PG108-R
Page 215
– 0xFC (byte offset)/2 = 0x7E (register ready)
• Length Field—The Length field in the WOL_Pattern_Configuration register specifies the number of clock
cycles required to compare a variable number of bytes, in the RX stream. The Length field uses a unit of
measurement specified in terms of memory arbiter clock cycles. Software should not program this field with
a byte value. The Length field should be programmed with the maximum number of clocks required to
compare the largest pattern size for the nine streams (10/100 mode only).
The programmer must use the following equation to calculate the number of clock cycles required to match
patterns at 10/100 wire-speed: (Length/2) * 3 MA clocks. The equation breaks down as follows:
– Determine the number of bytes in the RX Ethernet frame to compare. This value is a byte length.
– The WOL pattern checker can compare two bytes simultaneously. Divide length by two bytes and round
up to nearest integer value.
– The Ethernet controller compares 2 bytes every three memory arbiter (MA) clock cycles. Multiply
(Length/2) by three clock cycles.
• The following are example clock cycle calculations:
– Data stream length = 25 bytes
– 25 bytes/2 = 12.5 byte-pairs
– Round(12.5) = 13 byte-pairs
– 13 byte-pairs * 3 clocks/byte-pairs = 39 clocks (register ready)
– Data stream length = 83 bytes
– 83 bytes/2 = 41.5 byte-pairs
– Round(41.5) = 42 byte-pairs
– 42 byte-pairs * 3 clocks/byte-pair = 126 clocks (register ready)
WOL Streams
A stream is a comparison operation on RX frame(s). When the MAC is running at 10/100 Mbps wire speed, nine
different patterns can be compared against the RX frame(s). The Ethernet controller moves RX frame(s) into
nine parallel comparators, and the frame is matched simultaneously. The MAC is capable of filtering nine
different patterns in 10/100 modes. The WOL pattern checker breaks frames into 2-byte pairs, so all nine
comparators can begin matching data. In
, three Ethernet frames are compared against
the nine available patterns.
Note:
The Ethernet controller only supports one pattern stream at Gigabit wire speed, so the length
field will always be the largest pattern size.