In the area of industrial automation Profibus is one of the most successful FieldBus standards worldwide.
Profibus International formulates the technical and functional features of a serial FieldBus System that can network field Automation Devices from the lower (sensor/actuator level) up to the middle level (field level).
Profibus differentiates master and slave devices. The users requirements for an open communication systems are not fixed on one producer and lead to the specification and standardisation of Profibus protocol.
Profibus-DP is especially concepted to a fast, cyclic interchange with field devices. This system (protocols) distinguishes through very short response time and high interference immunity and replaces the cost intensive parallel signaling.
Profibus-PA is the version for use in process automation in the company-own area (Specification IEC 61158-2), eg. Large chemical plants and or oil + Petrochem installations.
For further reading see
PROFIBUS in Practice: Installing PROFIBUS devices and cables and
PROFIBUS in Practice: System Engineering, Trouble-shooting and Maintenance.