Principles; Chapter 5 Deployment Of The Cpu 821Xdpm - Adam 821x Manual

Chapter 5 Deployment of the CPU 821xDPM

Principles

General
Profibus-DP
Master and slaves
5-2
Profibus is an open fieldbus standard for building, manufacturing and
process automation. Profibus defines the technical and functional proper-
ties of a serial fieldbus system that is used to create a network of
distributed digital field automation equipment on the lower (sensor-/actuator
level) to middle performance level (process level).
Profibus comprises various compatible versions. The specifications
contained in this description refer to Profibus-DP.
Profibus-DP is particularly suitable for applications in production automa-
tion. DP is very fast, offers plug&play and is a cost-effective alternative to
parallel cabling between PLC and the decentral/distributed periphery.
Profibus-DP is conceived for high-speed data exchange on the sensor-
actuator level.
The data exchange is processed cyclically. During a one bus cycle the
master reads the input values from the various slaves and writes new
output information into the slaves.
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 like in the CPU 821xDPM 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 ADAM Profibus are modular slave
equipment, transferring data between the System 82xx 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.
ADAM 8000 Manual CPU 821x – Rev 1.1
CPU ADAM 821x