Siemens Welding System ST PCS 7 User Manual

PROFIBUS

Siemens ST PCS 7 · November 2007

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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.

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SIMATIC PCS 7 utilizes the benefits of the PROFIBUS from start 

to finish:

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Small planning and engineering overheads as well as low 

commissioning costs

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Optimum distributed system structure with low hardware and 

space requirements 

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Significantly reduced overhead for wiring, jumpering, distribu-

tion, power supply and field mounting

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High-speed communication with high measurement accuracy

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Efficient engineering, interoperability and replaceability of de-

vices through vendor-independent device description

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Short commissioning times through short loop tests, easy pa-

rameterization and the elimination of calibration work

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Bidirectional communication and high amounts of information 

permit enhanced diagnostics functions for fast fault locating 

and troubleshooting

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Optimum life cycle management through processing and 

evaluation of diagnostics and status information by an asset 

management system

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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:
• 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 DP

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RS 485: simple and low-cost electrical transmission system 

based on shielded two-wire cable.

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RS 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.

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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

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MBP (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.

PROFIBUS DP 

PROFIBUS PA 

PROFIBUS DP 

OLM OLM 

Industrial Ethernet 

RS 485-iS coupler 

Long distances 
with fiber-optic 

DP/PA link 

Automation system 

Ex isolation 
+ repeater 

© Siemens AG 2007