Editing Profibus (section)

== Origin ==
The history of PROFIBUS goes back to a publicly promoted plan from Marco Todaro for an association which started in Germany in 1986 and for which 18 companies and institutes devised a master project plan called "[[fieldbus]]".<ref name=book /> The goal was to implement and spread the use of a [[bit-serial]] field bus based on the basic requirements of the field device interfaces. For this purpose, member companies agreed to support a common technical concept for production (i.e. discrete or factory [[automation]]) and [[process automation]]. First, the complex communication protocol Profibus FMS (Field bus Message Specification), which was tailored for demanding communication tasks, was specified. Subsequently, in 1993, the specification for the simpler and thus considerably faster protocol PROFIBUS DP (Decentralised Peripherals) was completed. Profibus FMS is used for (non-deterministic) communication of data between Profibus Masters. Profibus DP is a protocol made for (deterministic) communication between Profibus masters and their remote I/O slaves.<ref name=PI4332 /><ref name=xiu3 />

There are two variations of PROFIBUS in use today; the most commonly used PROFIBUS DP, and the lesser used, application specific, PROFIBUS PA:
* '''PROFIBUS DP''' (Decentralised Peripherals)<ref name=mitchell /> is used to operate sensors and actuators via a centralised controller in production (factory) automation applications. The many standard diagnostic options, in particular, are focused on here.<ref name=PI8012 />
* '''PROFIBUS PA''' (Process Automation) <ref name=powel /> is used to monitor measuring equipment via a process control system in process automation applications. This variant is designed for use in explosion/hazardous areas ([[Electrical Equipment in Hazardous Areas#Zones (vapours & gases)|Ex-zone]] 0 and 1). The Physical Layer (i.e. the cable) conforms to IEC 61158-2,<ref name=iec61158-2/> which allows power to be delivered over the bus to field instruments, while limiting current flows so that explosive conditions are not created, even if a malfunction occurs. The number of devices attached to a PA segment is limited by this feature. PA has a data transmission rate of 31.25&nbsp;kbit/s. However, PA uses the same protocol as DP, and can be linked to a DP network using a coupler device. The much faster DP acts as a backbone network for transmitting process signals to the controller. This means that DP and PA can work tightly together, especially in hybrid applications where process and factory automation networks operate side by side.

In excess of 30 million PROFIBUS nodes were installed by the end of 2009. 5 million of these are in the process industries.<ref name=book />