Chapter 4 PROFIBUS communication
Manual VIPA System 200V
4-2
HB97E - CPU - RE_21x-2BM03 - Rev. 14/44
Overview
PROFIBUS is an international standard applicable to an open and serial
field bus for building, manufacturing and process automation that can be
used to create a low (sensor-/actuator level) or medium (process level)
performance network of programmable logic controllers.
PROFIBUS comprises an assortment of compatible versions. The following
details refer to PROFIBUS DP.
PROFIBUS DP is a special protocol intended mainly for automation tasks in
a manufacturing environment. DP is very fast, offers Plug'n'Play facilities
and provides a cost-effective alternative to parallel cabling between PLC
and remote I/O. PROFIBUS DP was designed for high-speed data commu-
nication on the sensor-actuator level.
The data transfer referred to as "Data Exchange" is cyclical. During one bus
cycle, the master reads input values from the slaves and writes output
information to the slave.
PROFIBUS distinguishes between active stations (masters) and passive
stations (slaves).
Master equipment
Master equipment controls the data traffic on the bus. There may be also
several masters at one PROFIBUS. This is referred to as multi master ope-
ration. The bus protocol establishes a logical token ring between the intelli-
gent devices connected to the bus.
A master of the CPU 21xDPM may send unsolicited messages if it has the
bus access permission (Token). In the PROFIBUS protocol masters are
also referred to as active stations.
Slave equipment
Typical slave equipment holds data of peripheral equipment, sensors,
actuators or transducers. The VIPA PROFIBUS are modular slave
equipment, transferring data between the System 200V periphery and the
leading master.
These devices do not have bus access permission in accordance with the
PROFIBUS standard. They may only acknowledge messages or transfer
messages to a master if requested by this. Slaves occupy a very limited
part of the bus protocol. Slaves are also referred to as passive stations.
PROFIBUS DP
Master and slaves
