PROFIBUS: Working, Types, Advantages & Applications Explained

Introduction

PROFIBUS (Process Field Bus) is a fieldbus communication standard widely used in industrial automation. Originally promoted by the German Federal Ministry of Education and Research (BMBF) in 1989, it is now commonly associated with Siemens. PROFIBUS should not be confused with PROFINET, which is an industrial Ethernet standard.

PROFIBUS is the most widely used industrial control network for automation, motion control, process control, and safety systems. More than 1400 equipment manufacturers worldwide support this protocol. It provides communication services across OSI layers 1, 2, and 7.

Two commonly used versions of PROFIBUS are:

• PROFIBUS-DP
• PROFIBUS-PA

PROFIBUS devices are categorized into masters and slaves. Masters control bus access and can send messages without external requests (active stations). Slaves are peripheral devices such as sensors, actuators, and transmitters, responding only when requested by the master (passive stations).

How Does PROFIBUS Work?

PROFIBUS communication is based on cyclic data exchange between PLCs (masters) and devices (slaves). Communication typically uses the PROFIBUS DP (Decentralized Periphery) protocol, supporting both cyclic and acyclic transfers.

In PROFIBUS DP, the master–slave method forms the core communication process. During a cycle, the master sends outputs to every slave and receives input data from each of them. Diagnostics for devices, modules, and channels are also handled in this cycle.

In a master-slave interaction, the master always controls the slaves unidirectionally. The master sends a request containing output data, and the slave responds with its input data. A bus cycle completes when the master polls all connected slaves in sequence. Apart from cyclic data exchange, acyclic communication is also possible. This is used for sending parameter data such as device configuration or settings. A master can read or write such data as needed to configure individual field devices.

Types of PROFIBUS

PROFIBUS has three major versions:

• PROFIBUS-DP – High-speed, low-cost communication for distributed I/O. It is widely used for automation control systems and replaces parallel signal transmission.

• PROFIBUS-PA – Designed for process automation. It supports intrinsic safety and allows both communication and power transmission over a 2-wire bus as per IEC 1158-2.

• PROFIBUS-FMS – A flexible, general-purpose communication system suitable for complex and lengthy communication tasks at the cell level.

Advantages of PROFIBUS

• Easy to use and highly adaptable
• Built on modular standards
• Supports continuous, discrete, and safety processes on the same bus
• Reduces the need for multiple systems by enabling hybrid automation
• Provides easier maintenance and troubleshooting
• Supports fast and flexible production
• Requires less wiring and hardware
• Allows operators to monitor device conditions continuously

Disadvantages of PROFIBUS

• Optimized mainly for short message transmission
• No power transmission capability in DP version
• More expensive compared to some other buses
• Data bandwidth limit of 244 bytes per node in PROFIBUS DP
• Installation cost is high due to special cables and distance extenders
• PROFIBUS-PA has a slow data rate (31.25 kbit/s)
• Low current flow through bus lines, though safer for hazardous areas

Applications of PROFIBUS

• Communication between field sensors and control systems
• Industrial automation and manufacturing
• Process industries (chemical, oil & gas, pharmaceuticals, etc.)
• High-speed and time-critical control applications
• Complex communication tasks in distributed systems