Frame Types

The use of this standard introduces a new format of frame, called an M-frame. M-frames are defined in the IEEE 802.3br standard as frames that have a special type of Start Frame Delimiter (SFD), called a Start mPacket Delimiter (SMD) and have a special type of CRC, called MCRC.

This new frame type is used by the MMSL to differentiate between the different types of traffic to determine whether:

• The frame is for the pMAC or eMAC
• An M-frame may consist of a full Ethernet frame or a fragment of an Ethernet frame

Frames to/from the eMAC are the same as regular Ethernet frames and when received will always contain a complete frame.

Frames to/from the pMAC use a different SFD and may be fragmented if a frame was required to be sent from the eMAC, in which case the pMAC frame is transmitted in between at least two pMAC frame fragments.