How to Program Siemens S7 300 Plc

Programming a Siemens S7-300 PLC involves using the STEP 7 software, to create and configure your program. Here are the general steps to program a Siemens S7-300 PLC:

Install Software:

Download and install the appropriate version of STEP 7 software on your computer. This software allows you to program and configure Siemens PLCs, including the S7-300 series.

Hardware Setup:

Connect your S7-300 PLC to your computer using the appropriate communication cable (e.g., MPI, Profibus, Ethernet).

Open a New Project:

Launch the STEP 7 software and create a new project.
Specify the hardware configuration, including the PLC model and any connected modules.

Program Structure:

Siemens PLC programming is typically done using ladder logic, similar to other PLC programming languages.

Creating and Editing Blocks:

In Siemens PLC programming, you create blocks for different tasks: OB (Organization Block), FC (Function Block), FB (Function), and DB (Data Block).
OBs are used for organizing the program execution sequence.
FCs and FBs are used to create reusable functions or subroutines.
DBs are used to store and manage data.

Programming Logic:

Use ladder logic diagrams to create your control logic.
Drag and drop instructions from the instruction set provided by the software to build your logic.
Instructions include timers, counters, comparison blocks, mathematical operations, and more.

Testing and Simulation:

You can test your program using the built-in simulation features of the software before downloading it to the physical PLC.
This helps identify errors and ensure the logic works as intended.

Online/Offline Mode:

You can work in either offline mode (without a physical PLC) or online mode (with a connected PLC). In online mode, you can monitor and modify the program while it’s running on the PLC.

Downloading to the PLC:

Once you’re confident in your program, you can download it to the PLC.
Ensure that you select the correct communication port and settings.

Monitoring and Debugging:

Use the monitoring tools to observe the program’s behavior in real time.
Debug any issues that arise and make necessary adjustments.


It’s essential to document your program thoroughly for future reference and troubleshooting.


Regularly back up your project files to prevent data loss in case of hardware failure or other issues.
Remember that this is a general overview of the process. Siemens STEP 7 software provides a user-friendly interface with detailed documentation and tutorials to guide you through the programming process for S7-300 PLCs. Always refer to the specific version of the software and the official Siemens documentation for the most accurate and up-to-date information.

2 thoughts on “How to Program Siemens S7 300 Plc”

  1. How do I configure (Program) my Siemens S7 1200 Plc to Connect (integred) the

    AMSAMOTION AMX-MT102IE, via Ethernet with Tia Portal.

    Can you make a Video or youTube to show details step by step.

    Thank you

    • To set these two steps on the PLC side
      1, remove optimized block access
      2, allow access from remote objects (check)
      On the touch screen side, DBBN is byte, DBN is word, DBDN is double word, for example, fill in DBN 1#0, the access address is DB1.DBW0


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