Unit 4

4.1 Introduction to Foundation Fieldbus

Foundation Fieldbus is a digital communication protocol used in industrial automation applications. It is a network of field devices and control systems that are connected through a digital communication system. The purpose of Foundation Fieldbus is to provide a standardized communication platform that enables interoperability between different automation devices from various manufacturers.

Foundation Fieldbus has four main layers that include the physical layer, data link layer, application layer, and user layer. Each of these layers plays a crucial role in the communication process.

4.1.1 Physical layer and wiring rules

The physical layer of Foundation Fieldbus is responsible for the physical connection between devices. It specifies the physical medium and electrical characteristics of the communication link. The wiring rules for Foundation Fieldbus require a twisted pair cable with a characteristic impedance of 100 ohms. The maximum cable length is 1900 meters, and the maximum number of devices on the network is 32.

4.1.2 Data Link layer

The data link layer of Foundation Fieldbus is responsible for ensuring error-free transmission of data between devices. It provides a reliable communication link by detecting and correcting errors that may occur during data transmission. The data link layer also manages the flow of data on the network to prevent congestion.

4.1.3 Application layer

The application layer of Foundation Fieldbus is responsible for the configuration, control, and monitoring of field devices. It provides a standardized set of commands that can be used to configure and operate different devices on the network. The application layer also provides a standard interface for accessing device data, allowing control systems to interact with field devices in a consistent manner.

4.1.4 User layer

The user layer of Foundation Fieldbus provides a user-friendly interface for configuring and monitoring the network. It allows users to interact with the network using graphical user interfaces (GUIs) or command-line interfaces (CLIs). The user layer also provides diagnostic tools that enable users to troubleshoot and debug network issues.

In summary, Foundation Fieldbus is a digital communication protocol that provides a standardized platform for interoperability between different automation devices. It has four main layers, including the physical layer, data link layer, application layer, and user layer, each of which plays a crucial role in the communication process.

Foundation Fieldbus has several benefits that make it an attractive choice for industrial control and automation applications:

1. Improved accuracy: Foundation Fieldbus provides high accuracy and precision for process control applications, as it uses digital communication instead of analog.

2. Real-time communication: Foundation Fieldbus supports real-time communication between devices, which is critical for many process control applications.

3. Integration: Foundation Fieldbus provides a common communication platform that enables integration of devices from multiple vendors.

4. Ease of use: The user layer of Foundation Fieldbus provides an intuitive and user-friendly interface for configuration, maintenance, and monitoring of the system.

5. Scalability: Foundation Fieldbus can accommodate a large number of devices, making it suitable for large-scale process control applications.

6. Increased efficiency: Foundation Fieldbus reduces the amount of cabling and wiring required, compared to traditional analog systems, which increases efficiency and reduces costs.

7. Advanced diagnostics: Foundation Fieldbus provides advanced diagnostic capabilities, allowing users to detect and diagnose faults in the system, reducing downtime and maintenance costs.

8. Increased reliability: The error detection and correction mechanisms built into the data link layer of Foundation Fieldbus increase the reliability of the system and reduce the risk of data loss or errors.

The data link layer of Foundation Fieldbus is responsible for ensuring reliable communication between devices in the system. This layer provides several important functions, including:

1. Data Framing: The data link layer defines the format and structure of the data being transmitted, ensuring that the data is transmitted in a standardized and recognizable format.

2. Error Detection: The data link layer provides error detection capabilities, allowing it to detect any errors that may occur in the transmission of data.

3. Error Correction: The data link layer also provides error correction capabilities, allowing it to correct errors that are detected in the data transmission.

4. Flow Control: The data link layer provides flow control capabilities, allowing it to regulate the flow of data between devices, ensuring that data is transmitted at a rate that can be handled by the receiving device.

5. Media Access Control: The data link layer provides media access control functions, allowing it to control access to the transmission media and ensuring that only one device is transmitting data at any given time.

The application layer of Foundation Fieldbus is responsible for providing the communication services and functions that are needed for process control and automation applications. This layer provides several important functions, including:

1. Process Control: The application layer provides process control functions, allowing it to control and monitor various process parameters and ensure that the process is operating within desired parameters.

2. Configuration and Management: The application layer provides configuration and management functions, allowing users to configure and manage the system and individual devices within it.

3. Monitoring and Diagnostics: The application layer provides monitoring and diagnostic functions, allowing users to monitor the system and diagnose any problems that may arise.

4. Data Logging and Recording: The application layer provides data logging and recording functions, allowing it to store data for later analysis and reporting.

5. Alarming and Event Handling: The application layer provides alarming and event handling functions, allowing it to generate alarms and handle events that occur within the system.