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Appendix
39
NetMax N8000 System Controller
Owner’s manual
Performance Specifications
According to the ISO 11898-2 standard, CAN-bus data transfer cabling has to be carried out
using Twisted-Pair cables with or without shielding providing a characteristic impedance of 120
Ω. Both ends of a CAN-bus need to be terminated with 120 Ω termination-plugs. The maximum
bus-length depends on the actual data transfer rate, the kind of data transfer cable being used,
as well as the total number of participants on the bus. The following table shows the most
essential requirements for CAN-networks consisting of up to 64 participants.
* With longer cables and many participants on the CAN-bus, termination resistors with higher
impedance than the specified 120 Ω are recommended to reduce the ohmic load of the interface
drivers and therefore the voltage drop between the two cable-ends.
The following table is meant for first assessment of necessary cable diameters for different bus
lengths and bus-participant numbers.
Additionally, the length of branch lines - for participants that are not directly connected to the
CAN-bus - is also of importance. For data transfer rates of up to 125 kbit/s, the maximum length
of a single stub cable should not exceed 2 meters. For higher bit rates a maximum length of only
0.3 meter is still permissible. The entire length of all branch lines should not exceed 30 meters.
General Note:
• As long as only short distances (up to 10 meters) are concerned, common RJ-45 patch
cables with a characteristic impedance of 100 Ω (AWG 24 / AWG 26) can be used for the
cabling inside of a rack mounted system.
• The previously outlined guidelines for network cabling are mandatory as far as the rack
mounted shelve interconnection or fixed installations are involved.
Bus Length (in m)
Date Transmission Cable
Termination (in Ω)
Max. Data Transfer
Rate
Resistance per
Unit Length
(in mΩ/m)
Cable Diameter
0...40 < 70 0,25...0,34 mm²
AWG23, AWG22
124 1000 kbit/s at 40 m
40...300 < 60 0,34...0,6 mm²
AWG22, AWG20
127 500 kbit/s at 100 m
300 ... 600 < 40 0,5...0,6 mm²
AWG 20
150...300* 100 kbit/s at 500 m
600...1000 < 26 0,75...0,8 mm²
AWG 18
150...300* 62,5 kbit/s at 1000 m
Bus Length (in m)
Number of Units on the CAN-Bus
32 64 100
100 0,25 mm² bzw. AWG24 0,34 mm² bzw. AWG22 0,34 mm² bzw. AWG22
250 0,34 mm² bzw. AWG22 0,5 mm² bzw. AWG20 0,5 mm² bzw. AWG20
500 0,75 mm² bzw. AWG18 0,75 mm² bzw. AWG18 1,0 mm² bzw. AWG17