Unlocking the Power of Advanced Program Blocks in SIMATIC S7-1200 Controllers

The SIMATIC S7-1200 PLC offers a suite of advanced program blocks designed for modular, flexible programming of complex automation tasks. Leveraging Function Blocks (FBs), Data Blocks (DBs), Organizational Blocks (OBs), and other specialized structures, you can build reusable code, streamline development, and improve system performance. This guide provides a comprehensive overview of program blocks in the S7-1200 and shares strategies for using them effectively.

Contents

1. Introduction to Program Blocks in SIMATIC S7-1200
2. Function Blocks (FBs) for Reusable Code
3. Data Blocks (DBs) for Data Storage
4. Organizational Blocks (OBs) for Program Execution
5. Using System Function Blocks (SFBs) and System Functions (SFCs)
6. Best Practices for Advanced Program Blocks

1. Introduction to Program Blocks in SIMATIC S7-1200 <a name="intro"></a>

Program blocks in the SIMATIC S7-1200 help structure your code, making it easy to organize, maintain, and troubleshoot. By using these blocks, you can create a modular program that enhances programming efficiency and consistency. Each block type serves a unique purpose, from data handling to execution control, creating a well-structured and flexible program.

2. Function Blocks (FBs) for Reusable Code <a name="fb"></a>

Function Blocks (FBs) allow you to design modular, reusable sections of code that perform specific tasks—such as motor control, sensor monitoring, or complex calculations. FBs can be invoked multiple times within a program, enabling you to build adaptable and efficient automation routines.

Key Features of Function Blocks:

• Instance Data Blocks (IDBs): Each FB can use an IDB to store data specific to that instance, ensuring independent operation of each FB call.
• Reusable Logic: FBs can be used across multiple projects, saving time and promoting consistency.
• Parameter Passing: FBs support input/output parameters, allowing you to pass data in and out of the block efficiently.

Example Application: Create an FB for motor control based on conditions such as temperature or load. Call this FB for each motor in your system, adjusting parameters as needed to match specific requirements.

3. Data Blocks (DBs) for Data Storage <a name="db"></a>

Data Blocks (DBs) provide structured storage for data independent of the main program logic. They support arrays, complex data structures, and variables, making data management efficient and organized.

Types of Data Blocks:

• Global Data Blocks (GDBs): Accessible from anywhere within the program, GDBs store data needed across various parts of the program.
• Instance Data Blocks (IDBs): These DBs are associated with specific FBs, allowing each instance to maintain unique data.

Example Application: Use a global DB to store temperature readings from multiple sensors. This data can then be accessed in various parts of the program for monitoring, control, or reporting purposes.

4. Organizational Blocks (OBs) for Program Execution <a name="ob"></a>

Organizational Blocks (OBs) manage program execution, controlling tasks like cyclic routines, startup processes, and interrupt handling. Each OB type has a specific function that provides flexibility in program flow.

Key Types of Organizational Blocks:

• OB1 (Main Program Cycle): This primary execution block runs continuously, driving the core control logic.
• OB100 (Startup): Runs once at startup, ideal for initializing variables or system settings.
• Cyclic and Time-Driven OBs: Triggered at specific intervals or by events, these are ideal for periodic tasks like data logging or status checks.

Example Application: Use OB100 to initialize sensor settings at startup and OB1 for the primary control loop of the automation process.

5. Using System Function Blocks (SFBs) and System Functions (SFCs) <a name="sfb_sfc"></a>

System Function Blocks (SFBs) and System Functions (SFCs) are predefined functions by Siemens for standard automation tasks, reducing the need for custom code and enhancing reliability.

Commonly Used SFBs and SFCs:

• SFB4 (TON): Provides an ON-delay timer function for timed control operations.
• SFB52 (ALARMS): Manages alarms and error handling, useful for alerting operators to system conditions.
• SFC20 (BLKMOV): Transfers data blocks efficiently, ideal for data handling in large applications.

Example Application: Use SFB4 to delay motor activation for safety and SFC20 to transfer data between DBs as part of a larger data management routine.

6. Best Practices for Advanced Program Blocks <a name="best_practices"></a>

To maximize the effectiveness of program blocks in SIMATIC S7-1200, follow these best practices:

1. Organize Program Logic with FBs and DBs: Break complex processes into manageable FBs, each with a corresponding DB. This modular approach enhances readability and simplifies troubleshooting.
2. Control Execution Flow with OBs: Use OB100 for initialization code and OB1 for real-time control. This separation makes the program flow organized and efficient.
3. Optimize Data Management with Global and Instance DBs: Store shared variables in global DBs and assign IDBs to FB instances, ensuring structured and manageable data storage.
4. Leverage SFBs and SFCs for Efficiency: Utilize Siemens’ predefined functions for common tasks like timing, alarms, and data handling to save programming time and boost reliability.
5. Document Your Code: Add clear comments and descriptions to each FB, DB, and OB. Proper documentation eases program maintenance, simplifies debugging, and facilitates teamwork.

Conclusion

Mastering advanced program blocks with the SIMATIC S7-1200 boosts programming efficiency, organization, and flexibility. By strategically using Function Blocks, Data Blocks, Organizational Blocks, and System Functions, you can create a robust and maintainable program. Follow best practices for structure and documentation to ensure your automation solution performs optimally, is easy to maintain, and can adapt to future requirements.