Profibus-Pa Features - Siemens DS Betriebsanleitung

1.1.2 PROFIBUS-PA Features

The PROFIBUS-PA (PA = Process Automation) permits bidirectional
communication between a bus master and the field devices via a screened
two-wire cable. The power supply to the two-wire few devices is transmitted
on the same cable (current
As a supplement to the EN standard 50170, the PNO (PROFIBUS user
organization) has defined the functions of the individual types of field de-
vices in a so-called profile description. This profile defines the minimum
functional requirements and optimum extensions. The device-internal
"Device management" is the basis for communication between the control
system and all devices - irrespective of their type and manufacturer.
The automation task is implemented using one or more PROFIBUS-PA lines
depending on the plant size and the required time response. A PROFIBUS-
PA line consists of the components shown in Figure 2.
Control room/switchroom
PLS, PC
Figure 2 PROFIBUS-PA architecture
Control is carried out by the central process control system PCS, or by a PC
in the case of low requirements. In general, the functions for DP-PA signal
conversion, bus connection and bus termination are unified in the device
"Coupler". A segment coupler or a link is used depending on the number of
PROFIBUS-PA field devices (FD) to be operated in the automation system
and the required time response. For transmission reasons, the bus must be
provided with an additional bus terminator at the furthest end.
SITRANS P
C79000-B5674-C207-1
I
in Figure 1).
PROFIBUS-DP
Coupler
T
Operating Instructions
Field
PROFIBUS-PA
FD FD
T
Additional
line terminator
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