■ Filter n Command Bit 3 specifies the address type of the pattern. When the bit is set, the pattern
applies to only multicast frames; when the bit is reset, the pattern applies only to unicast frame.
■ Filter n Command Bit 2 and Bit 1 are reserved.
■ Filter n Command Bit 0 is the enable for Filter n. If bit 0 is not set, filter n is disabled.
Filter n Offset
The Filter n Offset register defines the offset (within the frame) from which the filter n examines the
frames. This 8-bit pattern offset is the offset for the filter n first byte to be examined. The minimum
allowed offset is 12, which refers to the 13th byte of the frame. The offset value 0 refers to the first
byte of the frame.
Filter n CRC-16
The Filter n CRC-16 register contains the CRC_16 value calculated from the pattern and the byte
mask programmed to the wake-up filter register block.
20.3.10.2 Remote Wake-Up Frame Detection
When the MAC is in sleep mode and the remote wake-up frame enable bit,
WUPFREN
, is set in the
Ethernet MAC PMT Control and Status (EMACPMTCTLSTAT)
register, the normal operation is
resumed after a remote wake-up frame is received. The application writes all eight wake-up filter
registers, by performing eight sequential writes to the
Ethernet MAC Remote Wake-Up Frame
Filter (EMACRWUFF)
register. The Power Management (PMT) block supports four programmable
filters that allow support of different receive frame patterns. If the incoming frame passes the address
filtering of Filter Command, and if Filter CRC-16 matches the CRC of the incoming pattern, then the
MAC identifies the frame as wake-up frame. The Filter Offset determines the offset from which the
frame is to be examined. The Filter Byte Mask determines which bytes of the frame must be
examined. The 31st bit of Byte Mask must be set to zero. The remote wake-up CRC block determines
the CRC value that is compared with Filter CRC-16. The remote wake-up frame is checked only for
length error, FCS error, dribble bit error, MII error, and collision. In addition, the remote wake-up
frame is checked to ensure that it is not a runt frame. Even if the remote wakeup frame is more than
512 bytes long, if the frame has a valid CRC value, it is considered valid. The remote wake-up frame
detection is updated in the
Ethernet MAC PMT Control and Status (EMACPMTCTLSTAT)
register
for every remote wake-up frame received. If the
PMT
interrupt is enabled in the
Ethernet MAC
Interrupt Mask (EMACIM)
register, a
PMT
interrupt is asserted and the
EMACPMTCTLSTAT
register
can be read to determine reception of a remote wake-up frame.
20.3.10.3 Magic Packet Detection
The magic packet frame is based on a method that uses Advanced Micro Device's magic packet
technology to power up the sleeping device on the network. The MAC receives a specific packet of
information, called a magic packet, addressed to the node on the network. The MAC checks only
those magic packets that are addressed to the MAC or a broadcast address to determine whether
these packets meet the wake-up requirements. The magic packets that pass the address filtering
(unicast or broadcast) are checked to determine whether they meet the remote wake-up frame data
format of 6 bytes of all ones followed by a MAC Address appearing 16 times. The application enables
the magic packet wake-up by setting the magic packet enable bit,
MGKPKTEN
, of the
Ethernet MAC
PMT Control and Status (EMACPMTCTLSTAT)
register. The power management block constantly
monitors each frame addressed to the node for a specific magic packet pattern. Each frame received
is checked for a 0xFFFF.FFFF.FFFF pattern following the destination and source address field. The
power management block then checks the frame for 16 repetitions of the MAC address without any
breaks or interruptions. In case of a break in the 16 repetitions of the address, the PMT block again
1455
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller