SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
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 scans the 0xFFFF.FFFF.FFFF pattern in the incoming frame. The 16 repetitions can be anywhere in the frame, but must be preceded by the synchronization stream (0xFFFF.FFFF.FFFF). The device can also accept a multicast frame, as long as the 16 duplications of the MAC address are detected. If the MAC address of a node is 0x0011.2233.4455, then the MAC scans for the following data sequence:
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
00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55
00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55
00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55 00 11 22 33 44 55 CRC
The magic packet detection is updated in the EMACPMTCTLSTAT register for the received magic packet. 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 whether a magic packet frame has been received.