Answer / a.naresh

PROFIBUS is a vendor-independent open bus system. It has three types namely:
1.PROFIBUS-FMS (Fieldbus Message Specification
2.PROFIBUS-DP (Decentralized Periphery)
3.PROFIBUS-PA (Process Automation).

## The DP variant (decentralized periphery) is the high-speed solution of PROFIBUS. It has been designed and optimized especially for communication between automation systems and decentralized field devices. Therefore,PROFIBUS-DP requires less than 2 ms for the transmission of 1 Kbyte of input and output data. In this way even extremely time-critical communication tasks can be solved.PROFIBUS-DP communicates via cyclic data traffic exclusively.Each field device exchanges its input and output data with the automation device,within a given cycle time.

##In process engineering as well as in process automation,operation and monitoring tasks require a visualization device in addition to the automation device. This class-2 master is responsible for the various
start-up, parameterization and monitoring functions of up-to-date field devices.They require that device data be read or written during operation independent of the control cycle.
PROFIBUS-PA meets these special requirements of process automation.
The important characteristics of profibus PA are:
->intrinsically safe transmission techniques.
->field devices are powered over the bus cable,
->reliable data transmission, and
->interoperability (standardization of device functions).

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