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Elevator Core Reference Guide

Modbus RTU Connecting to the Drive

Modbus RTU - Physical Connectivity

The drive has a built-in RJ45 port for connection to Modbus RTU networks, this is highlighted in the table below.

Modbus Cable Pin Connections

Core_Modbus_RJ45_Pins.svg
Core_Unbranded_RJ45_Port_Location.svg

Caution

Always ensure 0V connection is present on the RJ45 cable.

Important

A network terminating resistor (120Ω) may be used at the end of the network to reduce noise.

Common Problems with Modbus Cable Connection

Below details common issues faced when trying to connect to the drive via Modbus

Problem

Solutions

Note

Drive will not connect to controller

  • Check cable is using the correct pin assignments

See diagram above for pin assignment

  • Check that the 0V pin is connected

Not connecting the 0V pin can cause port damage

Telegrams are being dropped

  • Check cables are routed properly

Excessive nosie can cause messages to be dropped

  • Use a terminating resistor

resistor should be 120Ω

Modbus RTU - Reading and Writing Parameters

All parameters within the drive can be accessed over Modbus RTU regardless of the setting of P1-01 - Primary Control Source.

For a full register map see the Parameter List Topics: Parameter Lists & Descriptions.

Below are examples of how to read and write to each parameter group over Modbus:

Reading/Writing Group 1 - 12 Parameters

Non Group 0 parameters can be accessed as per the following examples:

All parameter values can be read from the drive and written to, regardless of the operation state of the drive.

When accessing a drive parameter via Modbus, the Register number for the parameter is the same as the parameter number.

E.g. Parameter P1-01 = Modbus Register 101.

Reading Group 0 Parameters

The rule for reading Group 0 parameters is: Register Number = 10000 + Paramater Number

Example: Reading P0-32 over Modbus:

  • To read the value in parameter P0-32 (Back EMF measured value), read register 10000 + 32 = 10032.

Reading Group 0 Parameters with Sub Indexes

Rule for reading Sub Indexes is: Register = 11000 + (Par x 10) + Index

Example reading P0-38 Sub Index 4 over Modbus:

  • Register = 11000 + (38*10) + 4 = 11384

Warning

Sub indexes can only be read for Group 0.

Common Problems when Reading/Writing to Parameters

Below is a list of common problems with solutions:

Problem

Solutions

Note

Wrong parameter is changing

  • Check that you are using the correct Register Number

Check if the software uses 0 or 1 based addressing if 0 based is used all registers must have 1 subtracted from their original value.

Value Written not accepted

  • Check that the value you are writting is within the parameter range

Some parameters have a dynamic range to will change depending on other settings.

For example parameters P8-05 - P8-12 range will change depending on the settings of parameters P8-01 & P8-02.

Modbus RTU - Communication Setup Parameters

The following Parameters must be set in the drive for Modbus RTU communication to read & write to Parameters:

  1. Set the Modbus Slave Address in P2-01.

    The addresses of multiple devices on a network must not match each drive or device should have a different address.

    Parameter Number

    Parameter Name

    Default

    Available Settings

    Access

    Change During Run

    Modbus Register

    P2-01

    Modbus Slave Address

    1

    0 ... 247

    RW

    N

    201

  2. Set the Modbus Baud Rate in P2-02 to match the connected controller.

    Parameter Number

    Parameter Name

    Default

    Available Settings

    Access

    Change During Run

    Modbus Register

    P2-02

    Modbus RTU Baud Rate

    4: 115200bps

    0: 9600bps

    1: 19200bps

    2: 38400bps

    3: 57600bps

    4: 115200bps

    RW

    N

    202

  3. Set the Modbus RTU Data Format in P2-03 to match the connected controller.

    Parameter Number

    Parameter Name

    Default

    Available Settings

    Access

    Change During Run

    Modbus Register

    P2-03

    Modbus RTU Data Format

    0: n-1

    0: n-1

    1: n-2

    2: 0-1

    3: E-1

    RW

    N

    203

  4. Set the Modbus Response Delay.

    Parameter Number

    Parameter Name

    Default

    Available Settings

    Access

    Change During Run

    Modbus Register

    P2-06

    Modbus RTU Response Delay

    0 char

    0 ... 16 char

    RW

    N

    206

Parameter can be Read/Write regardless of the drives command source in Parameter P1-01.

When accessing a drive parameter via Modbus, the Register number for the parameter is the same as the parameter number so for example to access P1-02 the Modbus Register is 102.

Modbus RTU - Drive Control Parameters

The following Parameters must be set up to control the drive via Modbus RTU in addition to the communication Parameters in P2-01 - P2-06.

  1. Set the drive control source to 1:Modbus RTU in P1-01

    Parameter Number

    Parameter Name

    Units

    Default

    Available Settings

    Access

    Change During Run

    Scaling

    Size (Bytes)

    CAN Register

    CAN Sub Index

    Modbus Register

    P1-01

    Primary Command Source

    N/A

    0: Terminal

    0: Terminal

    1: Modbus RTU

    2: CANopen

    3: Reserved

    RW

    N

    N/A

    1

    2065h

    0

    101

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