I have a Modbus Plus Dual Cable Network in the system. I'm trying to connect HMI (Magelis iPC) with PCI85416NHM30032 MB+ PCI Adapter card to E984-785 Modicon Controller. There are some other nodes exists on the network (For Example: Some Workstations with MB+ ISA Cards).

I have observed following error while monitoring the Network statistics on MB Stat:
Cable A Framing Error
Cable B Framing Error

I'm getting data on my HMI but after some unpreditable time, it is missing for a while. Can anybody suggest a solution for this?

Posted By
Amitabh Todkar
[email protected]

 

<p>I have seen these problems before, it is mainly caused by using cable that is out of spec, or failure of the LAST physical drop on the cable to have a terminator on it.

<p>It can also be caused by electrical noise.
One thing is to try to find out where the problem is. MAKE SURE YOUR NETWORK IS WIRED SERIALLY. In other words there should not be any branches. Like this:
<pre>
1-2 2-3 3-4 4-5 etc.
</pre>
<p>Not like:
<pre>
1-2 2-3 3-4 4-5 5-6
3-8 8-9 etc.
</pre>
<p>Check all of your connections.
When I have a problem like this, I check for proper terminations. If I still have problems, I move the termination point to a midpoint of the wiring. If the problems clear up, you keep moving further away, if they are still present, move closer to the source.

<p>For a dual cable system to work properly, ALL devices should be dual cable devices.