Profibus DP and PA : It’s Not as Difficult as You Think

Profibus is the acronym for Process Field Bus.if you new here and want to know more Detail about Profibus here is the link :

Must Read : What is Profibus ? How Profibus Work ?

Profibus comes in three versions:

  • Profibus DP
  • Profibus PA
  • Profibus FMS

Must Read:Profibus DP vs Profibus PA vs Profibus FMS

Must Read : Profibus vs Profinet

Profibus DP


Profibus DP is designed for high-speed data communication at the device level.

The central controllers (for example, PLCs / PCs) communicate with their distributed field devices (I / O’s), drives (drivers), valves, etc., via a high-speed serial link.

Most of this data communication with the distributed devices is carried out cyclically.

In addition to performing cyclic functions, acyclic communication functions are available especially for intelligent field devices, allowing configuration, diagnostics and alarm handling.

As a feature, Profibus DP supports up to 126 nodes on a bus and allows multiple masters to be present on the network, as long as all slaves are associated with a single master.

There is no need for all slaves to be associated with the same master, since all masters are able to read slave information, however, only the associated master is able to carry out writing commands on the device.

Data exchange is normally cyclical and the bus cycle time is in the order of 10 ms.

Must Read : Profibus Cable & Profibus Connectors Tricks & Tips

Profibus DP is divided into three categories:

DPV0

Used in remote and simple equipment.

It has the following features:

  • Exchange of cyclical data between masters and slaves
  • GSD
  • Diagnostics.

DPV1

used when asynchronous data exchange is necessary or desired.

Its features are listed below:

  • Exchange of acyclic data between master and slave
  • Alarm management
  • Integration with EDDL and FDT
  • Fail safe,Functional blocks.

DPV2

used to implement high performance functions such as synchronous communication and data exchange in broadcast.

It has the following features :

  • Deterministic cycle time mode
  • Synchronous mode
  • Slave-slave communication for data exchange
  • Function publisher / subscriber,Clock synchronization and time stamp
  • Download and upload,Redundancy
  • Implementation of the HART protocol over DP.

Profibus FMS


Profibus FMS was created as a way to allow point-to-point multi-master communication, allowing up to 126 nodes in the network, where everyone can be a master.

Its focus is on higher levels of the automation pyramid, compared to other Profibus communication standards, since it provides communication between PLCs and SDCDs and, therefore, occupies a much larger bandwidth than Profibus DP or PA messages.

Recently, it has been replaced by systems that use protocols over Ethernet, since its main function is that of multi-master communication.

Profibus PA


The Profibus PA profile was developed in joint cooperation with standardizing institutions in the process industry (NAMUR) with the aim of replacing 4-20 mA analog communication and has the following special requirements for working in these application areas:

Standardized application profile for automation and process control and interchangeability of field devices between different manufacturers, that is, data reading standard (DS-33)

Insertion and removal of device stations without influencing the functioning of the network;

Feeding of the transmitter type devices, performed via the bus itself, according to the Profibus PA standard.

In this way, the PA protocol defines the parameters of the assets and the behavior of devices such as sensors and positioners independent of the manufacturer, thus facilitating the interchangeability of the device and the total independence of the manufacturer.

The Profibus-PA profile is based on the concept of functional blocks that are standardized in such a way as to guarantee interoperability between field equipment (Generic GSD).

The measurement values ​​and status, as well as the setpoint values ​​received by the field equipment in Profibus-PA, are transmitted cyclically with the highest priority via master class 1 (DPM1).

The parameters for visualization, operation, maintenance and diagnosis are transmitted by engineering tools (class 2 master, DPM2) with low priority through acyclic services via DP via C2 connection. A sequence of diagnostic bytes is also transmitted cyclically. The description of the bits of these bytes is in the equipment’s GSD file and depends on the manufacturer.

Once again, I hope this article has helped you in something and if you have any questions about triggering, post in the comments and I will reply as soon as possible.

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