PROFIBUS system

PROFIBUS family is another proven and popular fieldbus system in use in industrial automation system. The PROFIBUS system has three compatible versions that operate all together seamlessly. 

Positioning systems can use a network communication configuration, where the components operate as nodes on a network. Network communications protocols include ARCnet, CANbus, DeviceNet (a version of CANbus), Ethernet, PROFIBUS, IEEE 1394 (FireWire), IEEE 1451, Interbus-S, SERCOS, and Seriplex, among others. PC bus-type protocols include the normal backplane ISA/EISA (PC-XT/AT) connection for a PC, MAC PCI (Nubus) for Macintosh computers, Multibus, PC 104, PCI bus, cPCI bus (compact PCI), PCMCIA, VME bus, and VXI. 

A second example of encapsulation is a contactless operating plug-and-socket system with integrated electronics suitable for zone 1 application (Figs 6.37 and 6.38). The system allows power and data transmission with PROFIBUS DP/VI. The socket with an integrated pigtail cable is attached to a terminal box in increased safety - e Within the socket, the 24 V DC power... 

During international fieldbus standardization at the start of the 1990s a physical layer had been specified as IEC 61158-2 with an option for intrinsic safety. In the meantime, two standardized fieldbus systems comply with said standard Profibus PA and Foundation Fieldbus HI. These are the most important characteristics ... 

Single PROFIBUS or PROFINET standard Safety communication Conform to SIL 3/Category 4 Fast system configuration and commissioning... 

Stmctural details of PROFIBUS have been presented in Fig. IX/2.2.1-1 [2]. Like foundation fieldbus, here also there are different bus systems, viz. FMS, DP, and PA. 

As discussed earlier, in PROFISAFE, safety protocol is provided as a part of the communication protocols for both PROFIBUS/PROFINET. Therefore, end-users do not need separate networks BPCS and safety system instead they can integrate both the systems into a single network as shown in Fig. IX/2.2.3-1. 

High and low limit checks for transmitters have been in practice for quite some time, even when discrete instmmentations were in use. Now with the DCS it is very easy to monitor out of limits for the transmitter and open-circuit and short-circuit tests for sensors like resistance temperature detectors and thermocouples. Most of the transmitters are monitored for out of span (e.g., <4 or >20 mA). Also since smart transmitters have a diagnostic system, they also can detect faults and isolate them, that is, the output of a faulty transmitter could be inhibited generating an alarm. The transmitter is connected via HART/Profibus/fieldbus, and such detections are more explicit and well reported in the system. Also there exists a facility for the operator to select any transmitter manually. 

In recent time so-called field-bus interfaces (e.g. PROFIBUS, DeviceNet, LON) gain more importance. They may be used to integrate vacuum pressure transducers into complex process control systems without additional expense for cabling. 

Two well-known fieldbus systems are Profibus and AS-I (Actuator Sensor... 

PROFlsafe must ensure the necessary safety on a single charmel communication system while offering increased availability with redundant communication charmels. The aim is also to develop a solrrtion in the form of a PROFIBUS profile, using a specific format for the useful data (Figure 10.25). 

However, on PROFIBUS the system does not adeqrrately secrrre the data and ensures there are no errors. Safety messages take on a form sirttilar to standard messages, but the verification sequences of the frame arrd parity errsrrres the safety of the message. 

Communications Open systems Fieldbus/Profibus etc Limited, specialized Difficult with bus networks... 

Master system (MODBUS, PROFIBUS-DP) or OPC server to request common information, status lO signals, current values, presets and events... 

For process control applications the Siemens S7-400F series of safety certified PLCs includes the Profisafe communication system which allows safety data to be transmitted within the Profibus DP message flames. Field networks are then permitted to transmit control and safety critical data over the same media. Remote I/O modules include an AS interface gateway certified for safety duties. The network software and safety interface products have been certified by TUV for SIL-3 duties in accordance with lEC 61508. 

---