The ISO11898-2 standard specifies the interconnect to be a single twisted pair cable (shielded or unshielded) with 120 Ω characteristic impedance (ZO). Resistors equal to the characteristic impedance of the line should be used to terminate both ends of the cable to prevent signal reflections. Unterminated drop-lines (stubs) connecting nodes to the bus should be kept as short as possible to minimize signal reflections. The termination may be in a node but is generally not recommended, especially if the node may be removed from the bus. Termination must be carefully placed so that it is not removed from the bus. System level CAN implementations such as CANopen allow for different termination and cabling concepts for example to add cable length.
Termination may be a single 120-Ω resistor at the ends of the bus, either on the cable or in a terminating node. If filtering and stabilization of the common mode voltage of the bus is desired then “split termination” may be used, see Figure 10-4. Split termination improves the electromagnetic emissions behavior of the network by eliminating fluctuations in the bus common mode voltage levels at the start and end of message transmissions.