Difference Between Profibus-DP Bus and Profibus-PA Bus

PROFBUS is an international open fieldbus standard for high-speed and time-critical data transmission as well as for complex communication on a large scale.  

PROFBUS-DP is a communication protocol that is optimized for high-speed transmission of user data and is particularly suitable for communication between programmable controllers and decentralized I/O devices at the field level.  

PROFIBUS-DP is used for high-speed data transfer at the field level. The master reads the input information from the slave station cyclically and sends the output information to the slave station cyclically. The bus cycle time must be shorter than the program cycle time of the master (plc). In addition to cyclic user data transfer, PROFIBUS-DP also provides the acyclic communication required by intelligent devices for configuration. Diagnostics and alarm processing.  

Transmission technology: RS-485 twisted pair. Two-wire cable or fiber optic cable. Baud rates from 9.6Kbit/s to 12Mbit.  

PROFIBUS-PA for PROFIBUS process automation. PA connects automation systems and process control systems with pressure. The PA connects automation systems and process control systems with field devices such as pressure. humidity and level transmitters. the PA can be used as an alternative to 4-20mA analog technology. the PROFIBUS-PA has the following features.  

(1) Suitable for process automation applications line regulation allows interchangeability of field devices produced by different manufacturers.  

(2) The addition and removal of bus stations, even in intrinsically safe areas, does not affect other stations.  

(3) The PROFIBUS-PA segment for process automation and the PROFIBUS-DP segment for manufacturing automation are connected by couplers, and transparent communication between the two segments is possible. 

(4) Remote power supply and data transfer is accomplished using the same twisted pair as the IEC 1158-2 technology.  

(5) Explosion-proof "intrinsically safe" or "non-intrinsically safe" versions can be used in potentially explosive hazardous areas.  

1.PROFIBUS-PA Transmission Protocol  

PROFIBUS-PA uses the basic functions of PROFIBUS-DP to transfer measured values and status. The first layer of PROFIBUS-PA uses IEC 1158-2 technology, the second layer and the first layer are defined in the fourth part of the DIN 19245 series of standards.  

2. PROFIBUS-PA device protocols  

The PROFIBUS-PA specification guarantees the interchangeability and interoperability of field devices produced by different manufacturers and is an integral part of PROFIBUS-PA. The task of the PA specification is to select the functions of the various types of field devices that really need to communicate and to provide all the necessary specifications for these device functions and device behavior.  

Currently, the PA protocol has specified all common measurement transmitters and some other selected device types, such as:

(1) measuring pressure, liquid level, temperature and flow of the transmitter  

(2) digital inputs and outputs  

(3) analog input and output  

(4) valve  

(5) positioner