PROFIBUS

Communication at field level with PROFIBUS

Distributed peripherals such as remote I/O stations with their I/O modules, transmitters, drives, valves or operator terminals communicate with the automation systems (controllers) at field level through a powerful real-time bus system. This communication is characterized by:

• Cyclic transmission of process data
• Acyclic transfer of alarms, parameters and diagnostic data

PROFIBUS is predestined for these tasks because it enables high-speed communication with the intelligent distributed I/Os by means of a communications protocol (PROFIBUS DP) as well as communication and simultaneous power supply for transmitters and actuators (PROFIBUS PA).

PROFIBUS is simple, rugged and reliable, can be expanded online by further distributed components, and can be used in both standard environments and hazardous areas. It supports the coexistence of field devices from different vendors on one line (interoperability) as well as the vendor-independent exchangeability of devices from one profile family.

SIMATIC PCS 7 utilizes the benefits of the PROFIBUS from start to finish:

• Small planning and engineering overheads as well as low commissioning costs
• Optimum distributed system structure with low hardware and space requirements
• Significantly reduced overheads for wiring, patching, distribution, power supply and field mounting
• High-speed communication with high measurement accuracy
• Efficient engineering, interoperability and replaceability of devices due to vendor-independent device description
• Short commissioning times due to short loop tests, simple parameter assignment and the absence of calibration work
• Bidirectional communication and high information content permit enhanced diagnostics functions for fast fault identification and elimination
• Optimum life cycle management thanks to processing and evaluation of diagnostics and status information by the maintenance station

Users have numerous facilities for communication and line diagnostics, as well as for diagnostics of the intelligent field devices connected. Furthermore, the PROFIBUS is fully integrated into the global asset management with the maintenance station of the SIMATIC PCS 7 process control system.

For process automation, the following PROFIBUS functions are particularly relevant in addition:

• Integration of previously installed HART devices
• Redundancy
• Safety-related communication with PROFIsafe up to SIL 3 according to IEC 61508
• Time-of-day synchronization
• Time stamp

PROFIBUS transmission systems

PROFIBUS DP

• RS 485
  Simple and low-cost electrical transmission system based on shielded two-wire cable.
• RS 485-iS
  Intrinsically-safe electrical transmission system for hazardous areas up to Ex Zone 1 or 21, implemented using a shielded two-wire cable with a transmission rate of 1.5 Mbps.
• Fiber-optic
  Optical transmission system with glass or plastic fiber-optic cables, for fast transmission of large quantities of data in environments with high interferences or for covering long distances.

PROFIBUS PA

• MBP (Manchester coded; bus powered)
  Intrinsically-safe transmission system which permits simultaneous transmission of digital data and powering of the field devices by means of a two-wire cable. It is suitable for direct connection of devices in environments up to Ex Zone 1 or 21 and associated sensors/actuators in environments up to Ex Zone 0 or 20.