ProSoft Technology WRC-CANX - Manual (Page 19)

Western Reserve Controls WRC-CANX-xx Series 4
PUB 14.1 User’s Manual
15
5. Operation
The CANX accepts and stores messages received at either network connection and actively re-
transmits the messages to the other sub-net while providing 2500V isolation between the two sections of
the network. The two bus connections for each CANX are referred to as Sub-Network A and Sub-Network
B, and the two sub-nets are one logical network with isolation between them. The CANX may be used to
extend the maximum distance that a network can operate at any given speed. That is a CANX may be
used
• to extend the network beyond its absolute maximum length (e.g., 500 meters for
DeviceNet) at the slowest speed
• to implement a longer network for a given baud rate (e.g., pushing a 500K baud network
beyond 100 m for DeviceNet)
• to provide higher speed baud rates for a given network length
•
to extend the length of the drop cable (e.g., longer drops than 6 m for DeviceNet)
• provide 2500V electrical isolation between the 2 sub-nets
The CAN Bus is connected to each side of the CANX and each side receives its power and
signals from the Bus on its respective side.
Whenever a message is transmitted on the Bus to which CANX is connected, CANX receives the
message on the side where it was initiated and performs a store-and-forward of the message to the other
side. This action is performed for any valid CAN message independent of who generated it or to whom it is
addressed.
The CANX is not addressed as a specific device on the Bus and cannot be interrogated by other
nodes. It is transparent to all other nodes on the bus.
5.1. Application Notes
To help insure ease of installation and reliable operation of your system, the following guidelines
should be followed CANX installation in your CAN network.
You may install the Network A side or B Side of CANX toward the Bus Master.
The CANX takes its logic power from the A Side, but you may power up the CANX from either
side first.
There is approximately a 75 µsec propagation delay of the message through the CANX.
In autobaud mode, each side can autobaud from the other side or from the first message on
its own side.
CANX is not a grounded device and the Bus shield is not connected electrically to the device.
Therefore, follow appropriate wiring practices to eliminate noise and other problems.
5.1.1. CANX Theory of Operation
As described the CANX performs a store-and-forward operation on each message received. The
operation is described in this section.