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West Control Solutions KS 800 CANopen Interface Manual User Manual

Page 44

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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

µ

s

CANopen

800 kBd

50 m

1,25

µ

s

CANopen/DeviceNet

500 kBd

100 m

2

µ

s

CANopen/DeviceNet

250 kBd

200 m

4

µ

s

CANopen/DeviceNet

125 kBd

500 m

8

µ

s

CANopen

50 kBd

1000 m

*

)

20

µ

s

CANopen

20 kBd

2500 m

*

)

50

µ

s

CANopen

10 kBd

5000 m

*

)

100

µ

s

*

) 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.

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