CANopen data frame consists of :
SOF = start of frame (1 bit)
Arbitration field = 12 or 32 bits depending on whether 11 or 29 bit identifier is used (feature of the device)
Control field = 6 bits
Data field depends on mapping. Process data object can carry max 8 bytes. If each variable takes 2bytes then max content of 4 variables in data filed is possible.
CRC = control redundancy check (16 bits)
ACK = acknowledge (2 bits)
EOF = end of frame + intermission (7+3 bits)

Total: 47 bits + data filed (derived from number of variables mapped and their length).

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