How to Connect PLC and HMI. S7-200 & Delta DOP-B Communication

Connect plc hmi communication

Hi, Every Body. To connect and control PLC by HMI, you need making a connection (communication) PLC and HMI (set by the software and link by a cable). Today, I guide you the step by step to do it. The example in this post: connect PLC S7-200 and Delta HMI DOP-B (B07S411). The other PLCs & HMIs, you can do it with the same method.

Select the method for connect PLC and HMI

By reading the catalogue and checking the support connection of PLC & HMI use in your project. If it not support, you must change PLC type (or HMI type) to connect PLC and HMI

connect plc and hmi how to
DOP Series HMI Connection Manual

The example: I read the connection guide for Delta HMI DOP-B (“DOP Series HMI Connection Manual”). The document shows you, the methods connect DOP HMIs & PLCs (RS232, RS485…). Some devices may support Ethernet connection. Find your PLC type use (ex: S7-200).

-> I choose the RS485 method (via PLC Program Port) to connect S7-200 and HMI DOP-B.

connect s7-200 delta dop-b
Connect S7-200 and Delta HMI DOP-B

Set the connection parameters on software

The connection parameters for connect PLC and HMI: 

  • Interface: RS485, RS232, Ethernet…
  • COM port: COM1, COM2…
  • Baud rate: 9.6 kbps, 19.2 kbps, 187.5 kbps…
  • Data Bits: 7 bits, 8 bits
  • Stop Bits: 1 bit, 2 bits
  • Parity: Even, Odd…
  • Station Controller Address
  • Timeout, Retry Count, Delay time…

On Programmable Software of HMI

With the HMI Programs, the option name to set the connection parameters is different. Ex: With Delta, DOPSoft program is “Communication setting”. In normal, the default setting is ok (one HMI – one PLC).

delta dop b hmi communication
Communication Setting on DOPSoft V2.4

On Programmable Software of PLC 

With the PLC Programs, the option name to set the connection parameters is different too. Ex: With Siemens Step7 MicroWIN V4.0 program is “Communication port” in System Block. With the PLC Program, you make the parameters same with HMI Program above for connect PLC and HMI.

s7-200 communitation delta hmi
Communication Setting on Step 7 MicroWIN 4.0


S7-200 processes a longer period of internal program scanning or inputs an interruption command may slows down HMI response rate and cause “Must Retry” or “No Such Resource” error message. The communication Delay function is suggested to avoid this problem. The parameter setting unit is ms and suggested setting value is 10. The setting value should not be greater than 30 (By: “DOP Series HMI Connection Manual”).

The video guide connect PLC and HMI (S7-200 PLC and Delta HMI)

In the next post, I will show you: How to make the PLC & HMI connection cable.

Have fun!


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