Frame Transmission Overview - Motorola MC68824 User Manual

destination address of the frame. The address comparison for a non-group (individual) addressed
frame uses the individual address mask, this station's address, and the destination address of the
frame. Broadcast frames are always accepted. Once the station determines that it is to receive
the frame, the frame is transferred by DMA into the linked buffer portion of shared memory into
the appropriate priority queue. The TBC does all of the linking and transferring. After the frame
has been written into shared memory, an indication of its reception and its status are written into
the frame descriptor.
1.8.3 FRAME TRANSMISSION OVERVIEW
Data frames are transmitted from one of four transmission priority queues. Frames are only
transmitted out of the enabled priority queues. On reception of the token by the station, the TBC
checks the transmission queues for frames to be sent. If frames are present on one or more of
the queues, the TBC will send the frames until its allotted transmission time has expired, then
pass the token. Confirmation that a specific frame has been sent, along with the transmission
status is written into its frame descriptor.
MC68824 USER'S MANUAL
MOTOROLA
1-7
II