CAN / DeviceNet topology

CAN/DeviceNet is a 2-wire bus system, to which all participating devices are connected in parallel (i.e. using short drop lines) (Fig. DeviceNet Topology). The bus must be terminated at each end with a 120 (or 121) Ohm terminating resistor to prevent reflections. This is also necessary even if the cable lengths are very short!

Since the CAN signals are represented on the bus as the difference between the two levels, the CAN leads are not very sensitive to incoming interference (EMI): Both leads are affected, so the interference has very little effect on the difference.