Vega VEGACOM 557 Profibus FMS Bedienungsanleitung PDF herunterladen (Seite 47)

VEGACOM 557 Profibus FMS 47

Supplement

5.2 Special information on

PROFIBUS-FMS

PROFIBUS-FMS enables the communication

among automation devices as well as the

communication of the automation devices with

the intelligent field devices. Here the possible

functionality is more important than a short

system reaction time. In many applications

the data exchange is mainly made acyclically

on request of the application process.

PROFIBUS layer 7 (Application Layer)

Layer 7 of the ISO/OSI multilayer system

provides the communication services which

are available to the user. These application

services enable efficient, open data traffic

between application processes. The

PROFIBUS application layer is specified in

DIN 19 245 part 2 and consists of:

- Fieldbus Message Specification (FMS) and

- Lower Layer Interface (LLI).

Virtual field device (VFD) with object directory (OV)

Field device 1

VFD

Field device 2

VFD

logical connec-

tion

logical connec-

tion

For

communi-

cation, VFD is the

visible part of

the real field device

Real field device

Set value Formulation

Limit value

Virtual field device (VFD)

Level

Pressure Temperature

Object directory (OV)

Data type directory

Index Object code Meaning

1 Data type Integer8

2 Data type Integer16

……

6 Data type Floating Point

Statistic object directory

Index Object Data Internal Symbol

code type Address

20 VAR 1 4711 H Pressure

21 BAR 6 5000 H Temperature

22 VAR 2 100 H Level

!

FMS describes the communication objects,

the application services and the resulting

models from the communication partner’s

view.

LLI is used for adaption of the application

functions to the various characteristics of

PROFIBUS layer 2.

PROFIBUS communication model

An application process comprises all pro-

grams, resources and tasks not assigned to

a communication layer. The PROFIBUS com-

munication model enables the unification of

distributed application processes to one

complete process through communication

relationships.

The part of an application process in a field

device which can be reached via the commu-

nication is called virtual field device (VFD).

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 55 56

Kommentare zu diesen Handbüchern

Keine Kommentare