Mounting and wiring
CX8050, CX8051 - Embedded-PCs for
CANopen and CAN
27
Version: 1.4
Drop lines
Drop lines must always be avoided as far as possible, since they inevitably cause reflections. The reflections
caused by drop lines are not however usually critical, provided they have decayed fully before the sampling
time. In the case of the bit timing settings selected in the Bus Couplers it can be assumed that this is the
case, provided the following drop line lengths are not exceeded:
Baud Rate
Drop line length
Total length of all drop lines
1 Mbit/s
< 1m
< 5 m
500 kbit/s
< 5 m
< 25 m
250 kbit/s
< 10m
< 50 m
125 kbit/s
< 20m
< 100 m
50 kbit/s
< 50m
< 250 m
Drop lines must not have terminating resistors.
Star Hub (Multiport Tap)
Shorter drop line lengths must be maintained when passive distributors ("multiport taps"), such as the
Beckhoff ZS5052-4500 Distributor Box. The following table indicates the maximum drop line lengths and the
maximum length of the trunk line (without the drop lines):
Baud Rate
Drop line length with multiport
topology
Trunk line length (without drop
lines)
1 Mbit/s
< 0,3 m
< 25 m
500 kbit/s
< 1,2 m
< 66 m
250 kbit/s
< 2,4 m
< 120 m
125 kbit/s
< 4.8 m
< 310 m
CAN cable
Screened twisted-pair cables (2x2) with a characteristic impedance of between 108 and 132 Ohm is
recommended for the CAN wiring. If the CAN transceiver’s reference potential (CAN ground) is not to be
connected, the second pair of conductors can be omitted. (This is only recommended for networks of small
physical size with a common power supply for all the participating devices).
ZB5100 CAN Cable
A high quality CAN cable with the following properties is included in Beckhoff's range:
• 2 x 2 x 0.25 mm² (AWG 24) twisted pairs, cable colors: red/black + white/black
• double screened
• braided screen with filler strand (can be attached directly to pin 3 of the 5-pin connection terminal),
• flexible (minimum bending radius 35 mm when bent once, 70 mm for repeated bending)
• characteristic impedance (60 kHz): 120 Ohm
• conductor resistance < 80 Ohm/km
• sheath: grey PVC, external diameter 7.3 +/- 0.4 mm
Содержание CX8050
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