PM861 COM3 port RS232 communication getting stopped

Hi all,

I facing trouble in modbus communication using COM3 port of PM861 controller. I am using a RS232/485 converter for communicating 14 modbus serial devices. I am using cyclic enable for Mbconnect block where each block gets enabled for 8s and then turns off and the next device turns on. But the communication happens for about like 5hours without any problem and after that it stops totally. The communication only resumes only when I physically power off and on a modbus device.

Also if i try to enable all mbconnect block at same time, upto 8 device communication happens. Upon enabling of 9th device, entire communication stops and cannot be resumed even by turning the enable off. again have to power on and off a modbus device.

What can be the issue? Is it problem with controller settings or a problem with the RS232/485 converter itself?







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asked 2 months ago



Your Req parameter is too complicated and I think that is a problem.

As principle, each read block shoud be executed after the previous one is finished, so you can create logic for sequenced request of next read block after first read block generates Ndr or Error.

Some simple example is the following code, I'm using it successfully:

The right code for sequent execution of read blocks one after the other should be similar like this one:


answered 2 months ago


By kstoilov on 12/23/2017 | Like (0) | Report

connect blocks are usually always on

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