Profibus Overview; Figure 39. Profidrive - Eaton PowerXL DG1 Series VFD Communications Manual

PROFIBUS Overview

PROFIBUS is a vendor independent, open fieldbus standard
for a wide range of applications in manufacturing, process
and building automation. Vendor independence and
openness are guaranteed by the PROFIBUS standard EN 50
170. With PROFIBUS, devices of different manufactures can
communicate without special interfaces adjustment.
PROFIBUS can be used for both high-speed time critical data
transmission and extensive complex communication tasks.
PROFIBUS DP—Optimized for high speed and inexpensive
hookup, this PROFIBUS version is designed especially for
communication between automation and control systems
and distributed I/O at the device level. PROFIBUS DP can be
used to replace parallel signal transmission with 24V or 0 to
20 mA.
The PROFIBUS Family—PROFIBUS specifies the technical
and functional characteristics of a serial fieldbus system with
decentralized digital controllers can be networked together
from the field level to the cell level. PROFIBUS distinguishes
between master and slave devices.
Master Devices—Determines the data communication on
the bus. A master can send messages without an external
request when it holds access rights (the token). Master are
also called "active stations" in the PROFIBUS protocol.
Slave Devices are peripheral devices. Typical devices
include input/output devices, valves, drives and measuring
transmitters. They do not have bus access rights and they
can only acknowledge received messages or send messages
to the master when requested to do so. Slaves are also
called 'passive stations".
Profiles—The PROFIBUS DP protocol defines how user data
to be transmitted between stations over the bus. User data
are not evaluated by the PROFIBUS transmission protocol.
The meaning is specified in the profiles. In addition, the
profiles specify how PROFIBUS DP is to be used in the
"PowerXL" PROFIBUS Fieldbus board.
Leading manufacturers of drive technology have jointly
defined the PROFIdrive profile. The profile specifies how the
drives are to be parameterized and how the set points and
actual values are to be transmitted. This enables drives from
different vendors to be exchanged. The profile contains
necessary specifications for speed control and positioning. It
specifies the basic drive functions while leaving sufficient
freedom for application-specific expansions and further
developments. The profile describes the mapping of the
application functions for DP.
PROFIdrive consists of a general part and a bus specific part.
The following properties are defined in the general part.
Base Model
●
Parameter model
●
Application Model
●
PROFIBUS-DP External Communication Cards

Figure 39. PROFIdrive

The PROFIdrive base model describes an automation system
in terms of a number of devices and their interrelationships
(application interfaces, parameter access). The base model
distinguishes between following device classes.
Communication Services—Two communication services
are defined in the PROFIdrive profile; namely, cyclic data
exchange and acyclic data exchange.
Cyclic Data Exchange via a Cyclic Data Channel
Motion control system need cyclically updated data during
operation for open and closed loop control purposes. This
data must be sent to the drive units in the form of set points
or transmitted from the drive units in the form of actual
values, via the communication systems.
Acyclic Data Exchange via an Acyclic Data Channel
In addition to cyclic data exchange, there is an acyclic
parameter channel for exchanging parameters between
control/supervisor and drive units. Access to this data is not
time critical.
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