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Entry type: Application example Entry ID: 62830463, Entry date: 10/15/2018

Add-on blocks for Modbus/TCP communication

  • Entry
  • Associated product(s)
Modbus/TCP product blocks allow communication between S7-CPUs and devices from other manufacturers.

This involves the following products.

NameArticle number
Modbus/TCP CP2XV9450-1MB00
Modbus/TCP CP RED6AV6676-6MB30-3AX0
Modbus/TCP RED V22XV9450-1MB11
Modbus/TCP PN CPU2XV9450-1MB02


Table 1

Frequently, adaptations are required when implementing Modbus/TCP communication in a larger plant or system, for example:

  • For communication with Modbus/TCP blocks, more data should be sent to a partner than is possible using a single telegram. 
  • The Modbus data to be sent or read is saved in global data blocks. However, when using CFC, global data blocks are often not wanted.
  • In some plants and systems, it is specified that all the machine data - independent of the data type - is saved in a single data block.

These adaptations can be implemented in a user-friendly and convenient fashion by using the blocks provided in the "Additional Modbus Blocks" library. 

  • The "Job List" block allows several different Modbus telegrams to be cyclically processed.
  • "Data Collectors" blocks can be inserted in a CFC chart by dragging & dropping them. There, they are directly interconnected with the Modbus block to process Modbus data.
  • Using the "Marshalling Blocks" data that has been received or is to be sent with various data types (Holding Register, Input Register, Coils, Inputs) can be marshalled in a single data block.

"Additional Modbus Blocks" library for STEP 7 V5

Fig. 01

Documentation and library
  Documentation (1,7 MB)
 Registrierung notwendig  Library for STEP 7 V5 (67,9 KB)

The "Job List" library for STEP 7 V14 SP1 or higher
The "Job List" block is available as global library, also for STEP V14 SP1 or higher . Unzip the library to a directory of your choice. Open STEP 7. You can integrate the unzipped library under "Library > Global libraries > Open global library". The block is available in the SCL and STL programming languages.

Documentation and library
  Documentation (101,6 KB)
 Registrierung notwendig  Library for STEP 7 V14 SP1 (502,8 KB)

Additional information
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Last change
Update of the documentation of the "Additional Modbus Block" library for STEP 7 V5

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