Communication with PLC

Architecture Communication Interface


Communication interface architecture is based on the KOM process. KOM is the process of communication and processing of measured values which:

  • Enables communication with managing systems via serial communication lines, telephone modems, wireless communication by radio modems, BITBUS communication, etc.;
  • Enables simultaneous communication with various managing systems (Landis&Gyr PRU, Landis&Gyr PRV, SAE Control, Dragon-CS, Diamo-L, etc.);
  • Retrieves information about statuses and values of the monitoring technology parameters;
  • Performs the primary value processing – filtering, linearization, technical unit conversion, etc.;
  • Ensures setting of the required values and statuses in the technology.

The architecture of communication configuration in a single KOM process is divided into three logical levels: Link, Station and Measured Point.

It represents a communication interface providing communication.
It is usually a specific communication device (PLC). For some protocols, it can be a logical value grouping (OPC).
Measured Point
It is a specific parameter, the value of which is retrieved from/sent to a device.


Communication protocol Modbus




Communication protocol IEC 104






Modbus Communication Protocol


The following preview shows the communication configuration steps via Modbus communication protocol. It is used for data collection from an autonomous device, e.g.: a device for measuring heat, out of which values are read. Communication is performed via a serial link.

Run CNF:






Creating the Modbus_Client Line


After running the CNF program, find the Line object located in the left part of the screen.






Creating the Modbus_Client Station


In the left part of the screen, find and check a Station object. The current number of created stations will display in the right part of the screen.






Creating of the Modbus_Client Measured Point


With a Station, we will create a Measured Point. Select a Measured Point and set it so that it corresponds with the preview.





Creating the Modbus_Server Line


A Modbus_Server Line will be created in a similar way as a Modbus_Client Line.





Creating the Modbus_Server Station


With a new Link, we will create a Station. A Modbus_Server Line will be a parent for the Modbus_Server Station.



Creating the Modbus_Server Measured Point


With a new Line and Station, we can create a Measured Point.

Modbus communication results in transferring data from output (Modbus_server) to input (Modbus_client).





Communication protocol IEC 104

The following preview will show how to establish communication via the IEC 104 communication protocol. It is designed for communication between two systems, e.g. SCADA1 and SCADA 2. Communication is performed via TCP/IP.

We will create a demonstration of the communication performed via this protocol. We will create links, stations and measured points. For communication, it is necessary to create object in a correct order: Link -> Station -> Measured Point

Communication will result in data transfer via the IEC_104 communication protocol. Input values will be sent by IEC_104_Server (M.Y_OUT) and will display in an IEC_104_Client (M.Y_IN) output.



Creating a Line for IEC_104_Client


The first step is to create a Link that will be a future Station parent.






Creating a Station for IEC_104_Client


After creating a Link, we will create a Station that will be a future Measured Point parent.






Creating a Measured Point for IEC_104_Client



After creating a Station we will create a Measured Point.

When creating a Link, a Station and a Measured Point for the IEC_104_Server, we will follow the same steps as when establishing the IEC_104_Client.




Creating a Line for IEC_104_Server





Creating a Station for IEC_104_Server





Creating a Measured Point for IEC_104_Server


This preview will show the final value transfer from output to input of a device.


Topics: D2000, komunikacia-s-plc

Written by:

Boris Čonto

Boris Čonto