I-7242D user manual
I-7242D DeviceNet/Modbus RTU Gateway User’s Manual, July 2006, Version 1.1 11/124
2.2 Wire Connection
2.2.1 CAN bus wire connection
In order to minimize reflection effects on the CAN bus line, the CAN bus
lines have to be terminated at both ends by two terminal resistances. Based on
the ISO 11898-2 spec, each terminal resistance is 120
Ω
(or between
108
Ω
~132
Ω
). The length related resistance should have 70 m
Ω
/m. Users
should check the resistances of their CAN bus, before they install a new CAN
network as figure 2-2.
Figure 2-2 CAN Bus Wire Connections
Moreover, to minimize the voltage drop on long distance, the terminal
resistance should be higher than the value defined in the ISO 11898-2. Table
2-1 may be used as a reference.
Table 2-1 Relation between bus cable and length
Bus Cable Parameters
Bus
Length
(meter)
Length Related
Resistance
(m
Ω
/m)
Cross Section
(Type)
Terminal
Resistance
(
Ω
)
0~40 70
0.25(23AWG)~
0.34mm
2
(22AWG)
124 (0.1%)
40~300 <
60
0.34(22AWG)~
0.6mm
2
(20AWG)
127 (0.1%)
300~600 <
40
0.5~0.6mm
2
(20AWG)
150~300
600~1K <
20
0.75~0.8mm
2
(18AWG)
150~300
