Manual

KS 800 CAN-Interface
11.2 Bit rates and bus lengths:
The maximum useful bus length in a CAN network is determined by a variety of physical effects,
in particular:
The delay time of the connected bus nodes (with/without opto-couplers) and the delay
time of the bus cable (propagation delays),
various scanning times within a CAN bit cell due to the oscillator tolerances of bus nodes,
signal amplitude attenuation due to the DC resistance of the bus cable and the input
resistances of bus nodes.
When using ISO 11898-2-compliant transceivers, the bus mentioned below can be reached with
standard bus cables.
Nevertheless, the bus lengths may be considerably shorter with the high bit rates
(1 Mbit / 800 kbit) due to the number/speed of any opto-couplers (galvanic isolation)!
11.3 Practical bus lengths
CAN-Profil(s) Baud-rate Bus-length Nominal
Bit-Time
CANopen 1 MBd 30 m 1 µs
CANopen 800 kBd 50 m 1,25 µs
CANopen/DeviceNet 500 kBd 100 m 2 µs
CANopen/DeviceNet 250 kBd 200 m 4 µs
CANopen/DeviceNet 125 kBd 500 m 8 µs
CANopen 50 kBd 1000 m
*
) 20 µs
CANopen 20 kBd 2500 m
*
) 50 µs
CANopen 10 kBd 5000 m
*
) 100 µs
*
) With very long cables, using galvanic isolation and repeaters is indispensable.
For further information on bus lengths, see also standards CiA _DS-102_ (CANopen) or ODVA
_DeviceNet Specifications Volume I, Release 2.0_, in particular, Appendix A and B.
44 9499 040 49511