Modbus Communications; Introduction; Modbus Rtu Specification; Rj11 Connector Configuration - Invertek Optidrive Plus 3GV ODP-12037 Series User Manual

10. Modbus Communications

10.1.

Introduction

GV
The Optidrive Plus 3 can be connected to a Modbus RTU network via the RJ11 connector on the front of the drive.
10.2.

Modbus RTU Specification

Protocol
Error check
Baud rate
Data format
Physical signal
User interface
10.3.

RJ11 Connector Configuration

10.4.

Modbus Telegram Structure

GV
The Optidrive Plus 3 supports Master / Slave Modbus RTU communications, using the 03 Read Holding Registers and 06 Write Single Holding
Register commands. Many Master devices treat the first Register address as Register 0, therefore it may be necessary to convert the Register
Numbers detail in section 0 by subtracting 1 to obtain the correct Register address. The telegram structure is as follows:-
Command 03 – Read Holding Registers
Master Telegram Length
Slave Address 1 Byte
Function Code (03) 1 Byte
st
1 Register Address 2 Bytes
No. Of Registers 2 Bytes
CRC Checksum 2 Bytes
Optidrive Plus 3
Modbus RTU
CRC
9600bps, 19200bps, 38400bps, 57600bps, 115200bps (default)
1 start bit, 8 data bits, 1 stop bits, no parity.
RS 485 (2-wire)
RJ11 (see section 4.4 for more information)
Slave Response Length
Slave Address 1 Byte
Starting Address 1 Byte
st
1 Register Value 2 Bytes
nd
2 Register Value 2 Bytes
Etc...
CRC Checksum 2 Bytes
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GV
User Guide
Command 06 – Write Single Holding Register
Master Telegram Length
Slave Address 1 Byte
Function Code (06) 1 Byte
Register Address 2 Bytes
Value 2 Bytes
CRC Checksum 2 Bytes
Slave Response Length
Slave Address 1 Byte
Function Code (06) 1 Byte
Register Address 2 Bytes
Register Value 2 Bytes
CRC Checksum 2 Bytes
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