Modbus Communicationfor RTU Slaves

CompactLogix ControllerWith

1769 SM2 Module

By: Anish Shrivastava

Architecture

1769-L35E-CompactLogix5335E Controller

Modbus CableModbus Slaves

1769-SM2- Module

PCS ControllerPPI-402

SIPROTEC 4 7SJ61Multifunction Protection

Relay

Conzerv EM6400

AK-U0-RJ45-TB2P(RJ45 – RS485 Splitter)

Modbus RTU Network

Setting the Configuration Mode Switch in 1769 SM2 Module

Before installing the module, make sure its Configuration Mode Switch is correctly set.

SW1 Setting Description

CONT (Controller)back position

Default setting—The 1769-SM2 module uses the configurationdata downloaded from the controller on power-up and when thecontroller is placed in run mode.

PARAM (Parameter)front position

The 1769-SM2 module uses its internal parameter settings toconfigure the module.

SW2 Setting

Single Position (For Single drive per channel)

Multi-Drive Position (For Max 5 drives per channel or up 31 RTU slave devices per channel)

Select SW1 in Controller Position and SW2 in Multi-Drive Position.

Configuration and LogicM

od

ule

Con

fig

ura

tion

In

Log

ic

Mod

ule

Con

fig

ura

tion

In

Log

icConfiguration and Logic

Configuration and Logic1769-S

M2 M

od

ule

Con

fig

ura

tion

Data

For Channel

1

1769

-SM

2 M

odul

eCo

nfigu

ratio

n D

ata

Tabl

eConfiguration and Logic

Configuration and Logic

RTU Baud Rate Configuration RTU Format Configuration

e.g.: For baud rate 9600 bits/sec select value “2”.

e.g.: For None parity and 2 stop bits select value “3”.

Where The RTU format consists of threecomponents: data bits (8 data bits only), parity(None, Even or Odd), and stop bits (1 or 2).

For DSI I/O Config Select “5” for modbus RTU slave.

Use these data values to configure the configuration data table of SM2 module.

For RTU Rx Delay, RTU Tx Delay And RTU MSG Timeout select the values according to the load in controller and scan time of controller in such a way that the slave device has sufficient time to respond to the master.

Configuration and LogicLog

ic f

or

read

ing

Hold

ing

Reg

iste

r d

ata

of

RTU

Devic

es

Configuration and LogicLog

ic f

or

read

ing

Hold

ing

Reg

iste

r d

ata

of

RTU

Devic

es

Configuration and Logic

Path Format: Module Name, 2, Channel No.

Log

ic f

or

read

ing

Hold

ing

Reg

iste

r d

ata

of

RTU

Devic

es

Configuration and Logic

Refer to Notes

Log

ic f

or

read

ing

Hold

ing

Reg

iste

r d

ata

of

RTU

Devic

es

Notes

Slave Device ID: Can be configure for each slave device. (0-255)

Function Code: Can be differ according to the register type.(Such as 3-Holding Register, 4-Input Register)

Register Address and Length: May vary according to the slave device’s parameters.( For PCS Controller: Register Address is “3” and its data length is “1”.)

Please select the proper data mentioned above for slave devices otherwise communication fails.

For detailed information about these parameters please refer to the user manual of the particular slave device.

To check slave communication status and device parameters: use ModScan32 (3rd party software) if available.

AK-U0-RJ45-TB2P (RJ45 – RS485 Connector) Pin Out:

Clic

k H

ere

To S

ee E

xam

ple

References

1769 SM 2 Module User Manual

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1769-um013_-en-p.pdf

THE END