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!

Fig.8: DeviceNet topology

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.

Fig.9: Low interference through difference levels