Principles; Chapter 6 Deployment Of The Cpu 821Xdp - Adam 821x Manual

Chapter 6 Deployment of the CPU 821xDP

Principles

General
Profibus-DP
Master and slaves
6-2
Profibus is an international open fieldbus standard for building,
manufacturing and process automation. Profibus defines the technical and
functional properties of a serial fieldbus system that can be 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
automation. DP is very fast, offers plug&play and is a cost-effective
alternative to parallel cabling between PLC and the distributed/decentrali-
zed periphery. Profibus-DP is conceived for high-speed data exchange on
the sensor-actuator level.
The data exchange happens cyclically. During 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
operation. The bus protocol establishes a logical token ring between the in-
telligent devices connected to the bus.
A master like in the CPU 821xDPM is allowed to send unsolicited
messages if it has the bus access permission (Token). In the Profibus
protocol these masters are also referred to as active stations.
Slave equipment
Typical slave equipment holds data of peripheral equipment, sensors,
actuators, transducers. The ADAM Profibus couplers are modular slave
devices that transfer data between the System 8xxx 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 the respective master. Slaves are
also referred to as passive stations.
ADAM 8000 Manual CPU 821x – Rev 1.1
CPU ADAM 821x