BAS communication standards - Intelligent Buildings and Building Automation - page 84

FMS DP PA

FMS
profiles

DP
profiles

PA
profiles

DP extensions
DPV1, DPV2

DP basic
functions DPV0

Application Layer

Fieldbus Message
Specification (FMS)

Presentation Layer

Not used

Session Layer

Transport Layer

Network Layer

Link Layer Fieldbus Data Link (FDL)

IEC interface

Physical Layer RS-485/Fibre optic IEC 61158-2

Figure 5.4 PROFIBUS protocol model.

Besides BA, PROFIBUS has attracted applications across a wide range of
industries, including factory automation, robotics and machine tools, food
production, and chemical and petrochemical production.
All three PROFIBUS versions (DP, FMS and PA) use a uniform bus access
protocol. This protocol is implemented by layer 2 of the OSI Reference
Model as shown in Figure 5.4. In PROFIBUS, layer 2 is called the Fieldbus
Data Link (FDL). The FDL handles transmission protocols and includes
data security and error-detection measures. PROFIBUS can be implemented
over three optional transmission systems (cables), each with its own area of
applicability. These include: RS485, optical and shielded twisted pair.

5.5.2 Architecture and communication process

Data is exchanged in PROFIBUS systems using messages or telegrams that
pass between stations. A PROFIBUS network consists of several stations,
including masters or slaves . Master stations (also called active stations )
control the bus communication. Slave stations (also called passive stations )
can only respond to a request from a master. There are two types of master
station: Class 1 and Class 2. The Class 1 masters include PLCs, controllers,
SCADA stations, etc. The Class 2 masters include configuration tools, bus
monitors and diagnostics. Slaves include I/O blocks, transmitters, actuators,
valves and drives.