General Definition Of Profibus-Dp; Definition; Rs-485 Transmission System; General Information About Rs-485 Transmission Installation - Siemens COMBIMASTER 411 Operating Instructions Manual

Issue 03/02
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General Definition of PROFIBUS-DP

2.1

Definition

PROFIBUS is an international, open field bus standard widely used in the fields of
production and process automation. The bus is guaranteed brand-neutral and
open by virtue of its compliance with international standards EN 50170 and IEC
61158.
PROFIBUS-DP is a PROFIBUS communication profile optimized for high-speed,
time-critical data transmission at field level using low-cost connections.
PROFIBUS-DP is a suitable substitute for conventional, parallel 24 V signal
transmission systems in manufacturing, as well as for analog 4 to 20 mA signal
transmission systems in process automation.
PROFIBUS is a multi-master system, in other words, it is a bus on which several
automation, engineering or visualization systems can operate together with the
associated distributed field devices. In the context of PROFIBUS, master and
slave devices are defined as follows:
Ø Master devices control data traffic on the bus; they are also referred to as
"active" nodes. A master may transmit messages without prior receipt of an
external request provided that it has bus access authorization (token).
There are two classes of master:
♦ Class 1 master:
These are central automation stations (e.g. SIMATIC S5, S7 and
SIMADYN D), which exchange information with slaves in predefined
message cycles.
♦ Class 2 master:
These are programming, configuring or operator control and monitoring
systems that are used to configure or start up or monitor the plant in
operation.
Ø Slave devices are field devices such as drives (MICROMASTER 4), I/O
devices and valves. They never receive bus access authorization, i.e. they may
only acknowledge received messages or return information to a master on
request. Slave devices are also referred to as "passive" nodes.
2.2

RS-485 transmission system

Criteria such as high transmission speed and simple, low-cost installation are of
critical importance in the selection of the transmission system. The RS-485
requires a screened copper cable with twisted-pair wires.
Transmission speeds can be selected within the 9.6 kbaud to 12 Mbaud range. It is
set globally for all devices on the bus during system start-up.
2.2.1

General information about RS-485 transmission installation

All devices are connected in a bus structure (line). Up to 32 nodes (master or
slaves) can be interconnected within one segment. The bus is terminated by an
active bus terminator at the beginning and end of each segment. To ensure fault-
free operation, both bus terminators must have a voltage supply at all times. The
PROFIBUS Communication Module
6SE6400-5AV00-0BP0
Operating instructions
DEFINITION
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