Question
When I cycle power on my PLC, some of my HI 2151 Series units (HI 2151/20WC, HI 2151/30WC or the HI 2110WI) do not come online and show many retries, but others on the same network come online OK. When I change unit locations between one that does not come online with one that does, the problem stays with the location. What could be my problem?
Answer
On the HI 2151/20WC, HI 2151/30WC and the HI 2110WI, sometimes the length of your cable can cause problems with the communications of RIO devices. Different lengths of cable can cause signal reflections that can cause failed initialization of RIO communications. Check the RIO cable lengths, they should be at least 10 feet long between each device on the network.
Also, verify proper termination on both ends of the cable. This termination will vary depending on the baud rate you are using.
