Bit stuffing

For reliable data transport using a CAN bus it is mandatory that all the connected CAN stations work synchronously with each other. This means that each station inquires and processes the voltage level at the bus at the same time. Even the smallest deviation in time results in stations sending their bits at different times and the data traffic breaking down into chaos.
This synchronisation can be done in different ways. Since the CAN stations are only connected with one another over the bus line (normally twin wire), they also have to synchronise themselves over the bus line.

If a CAN station transmits 5 consecutive identical bits in one data or remote frame, a bit of opposite polarity is injected (stuffed). This inserted bit is used exclusively for synchronisation and is not interpreted as message content. This process is called "bit stuffing".