System Overview; Master/Slave System; System Configuration And Device Types - turck IO-LINK MASTER User Manual

PROFIBUS-DP

System overview

PROFIBUS is a manufacturer-independent and open fieldbus standard for a wide area of
applications in factory and process automation. Manufacturer independence and openness
are guaranteed by the international standards EN 50170 and EN 50254. PROFIBUS enables
communication of devices of various manufacturers without requiring particular interface
adaptations.
PROFIBUS-DP (Decentral Periphery) is designed for data transfer between the control and
the input/output level. TURCK BL20 stations support PROFIBUS-DP.
PROFIBUS-DP is the speed-optimized PROFIBUS version, specially designed for communi-
cation between automation devices and decentralized peripheral devices. PROFIBUS-DP is
suited to replace cost-intensive parallel signal transmission via digital and analogue sensors
and actuators.
PROFIBUS-DP is based on DIN 19245, part 1 and part 4. During the course of European
fieldbus standardization, PROFIBUS-DP has been integrated into the European fieldbus stan-
dard EN 50170.

Master/Slave system

PROFIBUS-DP is a master/slave system, which consists of a master (usually integrated in the
PLC) and up to 31 slaves per segment. During operation, the master constantly scans the
connected slave stations. Several masters may be connected within a single network; this
would then be classified as a multi-master system. In this case they pass on their transmission
permission (Token Passing).
PROFIBUS-DP uses a bit transmission layer (Physical Layer) based on the industrially proven
RS485 standard.

System configuration and device types

PROFIBUS-DP is suited for both mono-master or multi-master system configuration. Thus a
high level of flexibility in system configuration is guaranteed. The network comprises 126
devices max. (master or slaves).
Configurable system parameters include the number of stations, the assignment of the station
address to the I/O addresses, data consistence of I/O data, format of diagnostic messages
and the bus parameters used. Every PROFIBUS-DP system consists of different types of
devices.
One distinguishes between three device types:
DP master class 1 (DPM1)
This is a central control, which exchanges data in a defined message cycle with the remote
stations (slaves). Typical devices are, for instance, programmable logic controllers (PLCs) or
PCs.
DP master class 2 (DPM2)
Devices of this type are engineering, configuration or operating devices. They are used during
set-up, maintenance and diagnosis, to configure the connected devices, to evaluate para-
meters and to scan the device status.
DP slave
A PROFIBUS-DP slave is a peripheral device (I/Os, drives, transducers), which reads input
data and provides output data to the periphery. Of course, there are also devices which
provide only input or only output data. The input and output data volume depends on the
specific device and may comprise up to 244 bytes input data and 244 bytes output data.
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