BECKHOFF FC520x - Manual (Page 16)

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FC520x / CX1500-x520 15
BECKHOFF FC520x / CX1500-x520
3.2 Wiring the Bus System
3.2.1 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). 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.