Modbus communication issue- PM861 and CI853
I have a redundant configuration of PM861 and one CI853 for Modbus communication to a panel (Proface).
I am facing a problem of losing the Modbus communication 1 or 2 times per week.
After losing the Modbus communication if I do a power reset (total cabinet) communication will work for another 3 or 4 days.
I tried to replace the cable b/w CI853 and Proface panel. Also tried CI853 and Proface panel. Still the problem is not fixed.
As per me only possibility is MTU of CI853 or the firmware version.
Let me know is there any field alerts already available.
For your information whenever this Modbus communication losing still my controller is running. I can see the Run indication on controller. Also able to use the logic running inside the controller. I am able to go online with the controller. I took the controller log when I had the Modbus communication loss.
Any support is appreciated.
I have attached firmware version and compact control builder version.
As I know., there should not be a problem with a firmware or hardware.
Brake in communication could happen due to a different reasons, including simple disconnecting of the slave's communication cable. After te reason for communication lost is recovered, you need to reset the communication. You are doing now that when switch off / on of power supply.
I could recommend software reset of communication in case of fault:
Most probably you have MBConnect and MB Read / Write blocks for the communication with your pannel in your application.
Then the fault in communication you can "see" by Error output of MB Read / Write block (or miss of Ndr output for some longer time).
In this case you need just to disable (=false) En_C input of MBConnect block which establish communication for your COM port, resp. panel address.
The described could be easily realized by means for TP / TON functions and a simple logic.
There are many reasons that cause communication stops.
Check the following
1.ensure proper shield wire is earthed in both ends to ensure both master and slave in same ground level.
2.may be whenever the master try to poll d slave it's not responding in a timely manner.try to increase the number of resends default is 3 you increase upto 6.
3.check the controller log anything printed related to modbus communication.
4.check d controller load system.
5.always ensure mobus polltime should be greater than scan time
And always ensure removing modbus card in online needs controller reset as desgined so not to remove ci853 until it's faulty since PPP is not hot swap.
Which version of system is running?
Try to attach d controller logs,