PLC TO PLC Communication as Masster and Slave

Introduction

This tutorial will guide you through setting up PLC communication where one PLC acts as a master and the other as a slave. By following these steps, you will learn how to configure hardware, set up data blocks, and utilize system functions for effective data exchange between the two PLCs.

Step 1: Create a Project for Master-Slave Communication

• Open your PLC programming software.
• Create a new project for PLC Master to PLC Slave communication.
• Insert the master PLC and slave PLC into your schematic manager.
• Name the master PLC and the slave PLC accordingly for easy identification.

Step 2: Configure Hardware

• Insert the appropriate CPU for each PLC:
  • For the master, select CPU type 217 PN DP.
  • For the slave, select CPU type 37 TDP.
• Set the communication parameters for each PLC:
  • For the master PLC, configure it as a master.
  • For the slave PLC, configure it as a slave.

Step 3: Set Input and Output Addresses

• Define input and output addresses:
  • For the master PLC, set input address as 256 and output address as 256.
  • For the slave PLC, use the same addresses for consistency.
• Specify the length of data to send:
  • From the master, you will send 20 bytes.
  • From the slave, you will receive 32 bytes.

Step 4: Create Data Blocks

• Create two Data Blocks (DB) for each PLC:
  • For the master PLC:
    • DB 100 for sending data.
    • DB 101 for receiving data.
  • For the slave PLC:
    • DB 200 for sending data.
    • DB 201 for receiving data.
• Ensure DB 100 and DB 200 are parameterized for data transmission.

Step 5: Program Data Transmission

• To send data from the master to the slave, use the system function 50:

  SEND (Address: 256, DB: 100, Start: 0, Length: 20, Error Code: Word 4)
  

• To receive data from the slave to the master, use the system function 40:

  RECEIVE (Address: 256, DB: 101, Start: 0, Length: 32, Error Code: Word 4)
  

Step 6: Configure OB for Communication Errors

• Add Organizational Block (OB) 82 to handle communication errors:
  • This block will ensure that both PLCs are synchronized and can manage faults effectively.

Step 7: Download and Monitor the Program

• Connect your PC to both PLCs using the appropriate protocol.
• Download the configuration to both the master and slave PLCs.
• Monitor the data transfer to ensure successful communication:
  • Check the master PLC to confirm it is sending data.
  • Verify on the slave PLC that it is receiving data correctly.

Conclusion

By following these steps, you have successfully configured PLC communication between a master and a slave. This setup allows for efficient data exchange, which is essential in automated systems. As a next step, you may want to explore advanced error handling or integrate additional PLCs into your system for more complex automation tasks.