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Modbus protocol, 3 addressing, 4 overview of supported functions – KROHNE GFC 300 Modbus User Manual

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6

MODBUS PROTOCOL

10

GFC 300

www.krohne.com

03/2012 - 7312402100 - AD Modbus GFC 300 R01 en

6.3 Addressing

In the following tables the Modbus protocol addresses / data addresses are listed.

Some systems cannot use addresses above 9999. For these systems there is the possibility to
use the listed addresses but

• for Input Registers omit the leading 3 of 3xxxx;
• for Holding Registers omit the leading 4 of 4xxxx;
• for Input Registers replace the leading 20 of 20xxx by 9xxx.

Sometimes register numbers are asked for. The register numbers

register numbers

register numbers

register numbers can be calculated by adding a

1 to the protocol address and using a prefix according to the block:

• prefix 1 for coils
• prefix 3 for Input Registers
• prefix 4 for Holding Registers

6.4 Overview of supported functions

The following table shows Modbus functions supported by RS485 interface.

Function code

Name

Access to

hex

dec

01

01

Read Coil

Status of calibration functions (not applicable)

Counter status (start/stop)

03

03

Read Holding Register

Acyclic Registers

04

04

Read Input Register

Cyclic Register

05

05

Write Single Coil

Cold start

Warm start

Error reset

Start calibration function (not applicable)

Start / stop counter

08

08

Diagnostics

-

10

16

Write Multiple Register

Acyclic Registers

2B

43

Encapsulated Interface Transport

Transparent Channel

Read Device Identification