May 2022
Installation, Operation and Maintenance Manual
VCIOM-01493-EN Rev. 0
20
Section 7: Profibus DP Description
Profibus DP Description
Section 7: Profibus DP Description
Profibus is a vendor-independent, open fieldbus standard used in a wide range of
applications in process automation. Vendor independence and openness are ensured
by the international standards EN 50170 and EN 50254. The DP communication
profile is designed for data exchange at the field level. The central controllers (i.e., PLC)
communicate via a serial connection with field devices (as sensors and actuators). Data
exchange is mainly cyclic. The central controller (called master) cyclically reads the
input information from the field devices (called slaves) and cyclically writes the output
information to the slaves. In addition, the Profibus DP provides communication services
for parameterization, alarm handling, and monitoring of intelligent field devices. The
maximum number of master and slave devices in a bus segment is 32 without repeaters.
With repeaters, the number can be extended to 126 on one bus. The maximum cable
length depends on the speed of transmission. The higher the speed, the shorter is the
length. For instance, with baud rate 93.75 Kb/s, the max cable length is 1,200 m without
repeaters and 10,000 m with repeaters.
Mono-master or multi-master system configuration can be provided. Bus access is
controlled by a token passing procedure between masters and polling (master-slave
procedure) between master and slaves.
DP master class 1 (DPM 1):
This is the central controller that cyclically exchanges information with the field devices
Typical devices are PLC, DCS or PC.
DP master class 2 (DPM 2):
These devices are necessary for commissioning, maintenance and diagnostics.
Slave:
Field device, i.e. transmitters, actuators, drives, etc.
Figure 36 shows a Profibus DP configuration with two master devices and different
slave devices.
Figure 36
Logical token passing between master devices
Master devices
General
Drive
Transmitter
Slave devices
PLC
PC
EPI2 actuators