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Entry type: Application example Entry ID: 68202723, Entry date: 08/15/2019

Master-Slave Communication via a CM PtP using the Modbus RTU Protocol

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This application shows you how you can realize the function of a Modbus RTU master as well as that of a Modbus RTU slave in a S7-1500/ET 200SP automation system.

The application demonstrates how to:

  • configure the CM PtP RS422/485 HF as Modbus RTU master

  • configure the ET 200SP CM PtP as Modbus RTU slave

  • implement a Modbus RTU master and slave program in the program of a S7-1500 CPU

The example is designed such that the RTU master program as well as the RTU slave programs are realized together in one S7-1500 CPU. Here, the Modbus RTU master communication module is the S7-1500 CM PtP RS422/485 HF and the Modbus RTU slaves have been realized with the CM PtP communication modules of the ET 200SP. These Modbus RTU slaves in turn have been connected to the S7-1500 CPU via the ET 200SP head module. The two program parts (Modbus master and Modbus slaves) can be easily separated by you and can be adjusted to your own applications.

The figure below shows the hardware setup of the example.

Figure 01

Current version 2.1 for STEP 7 Professional V15.1 (TIA Portal)
  Documentation (1,3 MB)
 Registrierung notwendig  Project for STEP 7 Professional V15.1 (TIA Portal) (2,1 MB)   

Further Information
Communication via the CM PtPs of the ET200 SP and the S7-1500 using the Freeport Protocol
Master-Slave Communication with Modbus RTU Protocol for S7-300 and ET 200S Systems
How do you establish a MODBUS-RTU communication with STEP 7 (TIA Portal) for the SIMATIC S7-1200?

Last Changes
Correction of receive line initial state ("Modbus_Comm_Load".LINE_PRE)

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