Siemens ST PCS 7 manual Communication at field level with Profibus, Profibus transmission systems

© Siemens AG 2007

Communication

PROFIBUS

Introduction

■Overview

Industrial Ethernet

Automation system

Long distances with fiber-optic

PROFIBUS DP

OLM	OLM
	PROFIBUS PA
	DP/PA link

Ex isolation + repeater

PROFIBUS DP

RS 485-iS coupler

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 communica- tion is characterized by:

•Cyclic transmission of process data

•Acyclic transfer of interrupts, parameters and diagnostics 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 transmit- ters and actuators (PROFIBUS PA).

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

■Benefits

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

7 Small planning and engineering overheads as well as low commissioning costs

7 Optimum distributed system structure with low hardware and space requirements

7 Significantly reduced overhead for wiring, jumpering, distribu- tion, power supply and field mounting

7 High-speed communication with high measurement accuracy

7 Efficient engineering, interoperability and replaceability of de- vices through vendor-independent device description

7 Short commissioning times through short loop tests, easy pa- rameterization and the elimination of calibration work

7 Bidirectional communication and high amounts of information permit enhanced diagnostics functions for fast fault locating and troubleshooting

7 Optimum life cycle management through processing and evaluation of diagnostics and status information by an asset management system

■Function

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

In addition to all these properties, the following PROFIBUS func-
tions are particularly relevant to process automation:	9
• Integration of previously installed HART devices

•Redundancy

•Safety-related communication with PROFIsafe up to SIL 3 ac- cording to IEC 61508

•Clock synchronization

•Time tagging

On account of its exceptional characteristics, PROFIBUS is now established in all sectors of the production, process and hybrid industries and has become the most successful open field bus in the world.

PROFIBUS transmission systems

PROFIBUS DP

7RS 485: simple and low-cost electrical transmission system based on shielded two-wire cable.

7RS 485-iS: intrinsically-safe electrical transmission system for hazardous areas up to Ex zone 1, implemented using a shielded two-wire cable with a transmission rate of 1.5 Mbit/s.

7Fiber-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

7MBP (Manchester Coded; Bus Powered): intrinsically-safe transmission system which permits simultaneous transmission of digital data and powering of the field devices on a single two-wire cable. It is suitable for direct connection of devices in environments up to Ex zone 1 or 21 and associated sen- sors/actuators in environments up to Ex zone 0 or 20.

Siemens ST PCS 7 · November 2007

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