Campbell Hausfeld SDM-CAN User Manual

On receiving the frame data from the datalogger the SDM-CAN will convert and 
shift the data into the correct position and then place it into the read buffer which 
is set as a 64 bit frame. Depending on your program, you could then continue to 
build a frame or decide to transmit it onto the CAN-Bus. If you have completed 
the building of a frame then you have the choice to either transmit it onto the 
CAN-Bus or set it up as a Remote Frame Response. For the transmitted frames, 
the SDM-CAN will set a flag in the buffer to indicate new data is ready for 
transmission. The SDM-CAN will scan the buffers, checking this flag in each 
buffer that is set for transmission. When it finds a flag that is set, it will first check 
if  the transmitter is busy, and if it is will wait until it is free. The frame will then 
be transferred to the transmitter which will transmit it onto the bus. Finally the 
transmit data flag will be cleared. 

When a frame is set up for a remote frame response, the frame is transferred into 
the working buffer ready for reception of a Remote Frame Request. When a 
Remote Frame Request is received, and is accepted as a valid frame, the        
SDM-CAN will find the relevant buffer, and will then set the data transmit flag. 
From then on it will follow the normal frame transmission protocol as described 
above.