Vega VEGACOM 557 Modbus protocol Bedienungsanleitung PDF herunterladen (Seite 30)

30 VEGACOM 557 Modbus

on

PC

VEGALOG

571

!

4.3 Measured value image when

connected to LOGBUS

The addressing of the measured values for

Modbus systems is "word orientated“. In

VEGACOM 557 a meas. value is represented

by two words, the first word includes the real

meas. value, the next higher word the re-

spective status information. In the standard,

the designation “register word” is also used

instead of the term “word”. The addressing is

either made via existing library enquiries of a

PLC (e.g. Modicon) or by direct generation of

Modbus telegrams.

Measured value image when connecting to VEGALOG

571

DCS output 1

DCS output 2

DCS output 3

DCS output 255

Meas.

value

z

Meas.

value

x

Meas.

value

y

Examples of valid register word addresses

are shown in the following demonstration.

Especially when using Modicon, make sure

that the register address for the library en-

quiry is increased by 1 with respect to the

transmitted address on the Modbus.

VEGALOG 571 can administrate up to 255

measurement loops. For transmission of

measured values from a measurement loop,

VEGALOG makes up to 255 DCS outputs

available.

One or several DCS outputs with any index

can be allocated to these measurement

loops. The configuration of VEGALOG 571 is

made with the VEGA adjustment software

VVO. You define, via the selected PC/DCS

output, where the respective measured val-

ues can be collected within the intermediate

storage in VEGACOM 557.

Note:

When addressing register words, all ad-

dresses between 0 and 65 535 can be used

with VEGACOM 557. When accessing the

intermediate storage, VEGACOM 557 gener-

ally uses only the last 3 digits of the address.

This results in the following conversion table:

Register Register Register

address in address on address in

Modicon Modbus VEGACOM

557

30 001 30 000 000

30 017 30 016 016

34 001 34 000 000

34 017 34 016 016

Data image in VEGACOM 557

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 67 68

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