User`s manual

Western Reserve Controls WRC-CANR-DF-DN User’s Manual
PUB 14.1 Series 3
10
A CAN-Bus system must be terminated at each end of a copper trunk line. The host
controller and the last node device or WRC CAN-Bus Extender on the network must always be terminated
to match impedance and eliminate reflections, even if only two nodes are present. Follow the information
below when using a CANR-DF.
The CANR Series 3 has a built-in terminator which can selectively included or omitted from the
network. To include the on-board terminator (on the DeviceNet side), install jumper W1; or remove the W1
jumper if the on-board terminator in not desired. The CANR is shipped from the factory with the jumper
installed. See Figure 4-1 for the location of the jumper.
Trunk line use:
For the purpose of network termination, the CANR-DF is treated as the last node on the copper
section of the trunk network (side A) to which it is connected. Therefore, when a CANR-DF is used directly
in a trunk line, it must be terminated on side A. The terminating resistor built into the CANR-DF at W1 must
be installed, or another terminator at the end of the line could be used in the place of the W1 terminator.
Drop line use:
When CANR-DF is used in a drop line line (the Network A side is toward the main trunk), the
Network A connection must not be terminated. The user must remove the built-in terminator by removing
the jumper plug at W1.
Some specifications for the terminating resistor are:
Table 4-8 Terminating Resistors
DeviceNet SDS
121 ohm 120 ohm
1% metal film 2%
1/4 watt 1/4 watt
Important: Per the DeviceNet and SDS specs -- do not terminate devices on drop lines.
4.5.3. CAN-Bus Connection Wiring
The CANR-DF uses the round, mini-style connector on the copper side A and standard ST
connectors on the fiber side B.