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[KB783]Modbus functions used according to frame data type

Tags: Cimway, Modbus TCP/IP, Protocol

Data acquisition
10 years ago
By RM
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Applies to:

PcVue prior version 16
Summary:

This article gives the correspondance between the Modbus Ip function used and the PcVue Frame data type
Details:

Please find the correspondance table between the Modbus Read function and the frame type you have to configure in the supervisor to use the corresponding Modbus Ip function.

Please note that most of the frames you will configured are Word I/O and Bit I/O since you access the internal data of the PLC and not directly its inputs

Modbus Function Descriptions [Max length] Frame Data type
1 (0x01) Read Coil [2000]

For internal bit or Digital output

 BIT I/O
2 (0x02) Read Input Status [2000]

For Digital input only

 BIT I
3 (0x03) Read Holding Register [125]

For internal word or output word 

 Word I/O

DWord I/O LMsb – DWord I/O MLsb

Real I/O LMsb – Real I/O MLsb

Wordbit I/O LM – Wordbit I/O ML
4 (0x04) Read Input Register [125]

For Input word only 

 Word I

DWord I LMsb – DWord I MLsb

Real I LMsb – Real I MLsb

Wordbit I LM – Wordbit I ML
5 (0x05) Write Single Coil BIT I/O
6 (0x06) Write Single Register Wordbit I/O LM – Wordbit I/O ML
15 (0x0F) Write Multiple Coils [1968] BIT I/O
16 (0x10) Write Multiple registers [123] Word I/O

DWord I/O LMsb – DWord I/O MLsb

Real I/O LMsb – Real I/O MLsb

Wordbit I/O LM – Wordbit I/O ML

Created on: 13 Apr 2015 Last update: 02 Dec 2024