PDM_OpMaProfi_03_us.FM
page 10 field bus PROFIBUS-DP PacDrive™ M
3 Overview
Korrekturausdruck
PROFIBUS-DP
This PROFIBUS variant, which is optimized for speed and low con-
nection costs, is designed especially for the communication
between automation systems and decentralized peripherals on field
level. PROFIBUS-DP is suitable as a substitute for conventional
parallel signal transmission with 24 Volt or 0-20 mA.
Basic features
PROFIBUS determines the technical and functional features of a
serial field bus system in which automation appliances located in
different places can be networked from field level to cell level. PRO-
FIBUS differentiates between master and slave units.
Master units determine the data transfer on the bus. A master may
send messages without external request if it has a bus token. In the
PROFIBUS protocol, masters are also called active participants.
Slave units are peripherals. Typical slave units are input/output
devices, valves, drives and measuring transducers. They have no
bus token, i.e. they can only acknowledge received messages or
transmit messages to the master on request. They require only a
small part of the bus protocol, which makes the implementation
fairly simple.
The MAx-4 PacController can be a master and/or slave.
The PROFIBUS module is plugged into the MAx-4 PacController
and served from there.
3.2 PROFIBUS-DP
PROFIBUS-DP is designed for fast data exchange on field level.
The central control units, such as PLC/PC, communicate with
decentralized field units such as I/O, drives and valves via a fast
serial connection. The necessary communication functions are
determined by the PROFIBUS-DP basic functions according to EN
50 170.
For parameter setting, diagnosis and alarm handling while cyclic
data transfer is in progress, additional acyclic communication
functions are needed for intelligent field units. They are defined in
the PROFIBUS directive no. 2.042 and will be explained in chapter
3.2.
Basic Functions of PROFIBUS-DP
The central control (master) cyclically reads the input information
from the slaves and writes the output information to the slaves.
Besides the cyclical transfer of useful data, PROFIBUS-DP also
features efficient functions for diagnosis and commissioning. Data
