ProSoft Technology WRC-CANX - Manual (Page 32)

Western Reserve Controls WRC-CANX-xx Series 4
PUB 14.1 User’s Manual
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8. How do I determine the location in my network at which I might need a WRC CANX or CANR?
•
Drop Line: The WRC CANX or CANR should be used in a drop line when you would like to extend
the drop more than 6m.
•
Trunk Link: The CANX or CANR should be used in the main trunk line when you desire to extend
a network beyond its maximum length (e.g., 500 meters for DeviceNet at 125K baud rate or
beyond 100 m for DeviceNet at 500K baud rate)
•
Differences in baud rate: The WRC CANX and CANR can pass communications from two
different baud rates back and forth with each other (e.g., Network A at 125K and Network B at
500K)
• Isolation: The CANX and CANR can provide 2500V electrical isolation between 2 sub-nets.
9. Does the WRC CANX or CANR act as a node on the network?
No. The WRC CANX and CANR are repeaters, which remain completely invisible to the master
device or PLC. The unit does not have a MAC ID. It will only pass messages through (without
modifying them) and cannot generate its own messages.
10. How much power does my WRC CANX or CANR require and what is the best means of
supplying it?
The WRC CANX and CANR should be powered with 11-25Vdc provided by the DeviceNet network,
or other DC power supply. The WRC CANX and CANR Series 4 consume approximately 1.5W
(60mA at 25Vdc). Power is typically taken from the bus on each side and each side (A and B)
requires power. Power applied to the A Side powers the entire unit except the B Side isolated
transceiver. If isolation is not required for your application, then the power line may be jumpered
from side A to side B. Care must be taken that the power supply is capable of handling the entire
load on both sides of the CANX.
11. Is there a limit to the number of times a network can be extended using a WRC CANX or
CANR?
There is no technical limit to the number of WRC CANXs or CANRs that can be placed in a
network. The number of extenders in a network is generally dictated by the length limitations, due to
the operation baud rate, of the network desired. Also, although the CANX and CANR have very
small propagation delays, their delay times add up when there are multiple units on one network.
For this reason, the master device’s EPR time should be adjusted to be greater than the message
transmission time (which includes the transmission time on the data lines plus the propagation delay
of the CANXs or CANRs) when adding several CANXs or CANRs to your network.
12. How do I know how many WRC CANXs or CANRs my application will require?
While there is no set formula for determining the number of WRC CANXs or CANRs, the length of
the network you are trying to create is most likely the dictating factor in the answer to this question.
The lengths of drop and trunk lines must follow CANbus guidelines for the selected protocol. A
CANX or CANR should be added in the network whenever you desire to extend the length of a drop
or trunk line beyond the normal maximum allowed length. Please refer to the WRC CANX or CANR
User’s Manual section “Cable Lengths” for more information on the allowed cable distances for each
baud rate and network protocol.
13. What do the LEDs on the WRC CANX or CANR tell me about how the unit(s) are behaving?
The Network LEDs on a CANX will be green and blinking slowly if a connection is established, but
no messages are being transmitted/received. They will be solid green when messages pass. These
same LEDs will be red if there is no connection. The same diagnostics apply for the NSA LED of a
CANR, but the NSB LED of a CANR indicates the status of the remote unit and whether the fiber