User`s manual

Western Reserve Controls WRC-CANX-xx Series 3

PUB 14.0 User’s Manual

Table 5-6 Network Maximum Lengths - SDS

Baud Rate

Trunk Line Length

(maximum)

Drop Length

(maximum)

No. Nodes

Meters Feet Meters Feet

125 Kbits/s 457.2 1500 3.6 12 64

250 Kbits/s 182.8 600 1.8 6 64

500 Kbits/s 91.4 300 0.9 3 64

1 Mbits/s 22.8 75 0.3 1 32

SDS has a limit of 32 nodes per network for any baud rate. The CANX does not count as an

addressed device.

5.5.2. Network Termination

A CAN-Bus system must be terminated at each end of the trunk line. The host controller and

the last device (CAN-Bus Extender or other DeviceNet node) on the network section must always be

terminated to eliminate reflections, even if only two nodes are present. Follow the information below when

using a CANX.

The CANX Series 3 has built-in terminators which can selectively included or omitted from the

network. To include the on-board terminator on side A, install jumper W1; or remove the W1 jumper if the

on-board terminator in not desired. For the side B sub-network, install or remove jumper W2. The CANX is

shipped from the factory with the jumpers installed.

Trunk line use

For the purpose of network termination, the CANX is treated as the last node on the section of the

trunk network to which it is connected. Therefore, when a CANX is used directly in a trunk line, it must be

terminated on both the Network A and Network B sides. You must also place a terminating resistor on the

other end device of Network A and on the last device on Network B side of the trunk line.

Drop line use

When CANX is used in a drop line (the Network A side is toward the main trunk), the Network A

connection is not terminated. In this configuration the Network B section is considered as an independent

bus line electrically. The CANX, as the first node in this new bus line and must be terminated, and the last

device on the line must also be terminated.

Some specifications for the terminating resistor are:

Table 5-7 Terminating Resistors

DeviceNet SDS

121 ohm 120 ohm

1% metal film 2%

1/4 watt 1/4 watt