Allen Bradley MicroLogix 1000 Connection Guide

Introduction

This article is a guide to connect an Allen Bradley MicroLogix 1000 PLC to Fernhill SCADA.

The Allen Bradley MicroLogix 1000 PLC has a single serial port which can be used to communicate with Fernhill SCADA. The serial port on the PLC is an 8 pin mini-DIN socket located on the left side of the PLC.

To connect a MicroLogix 1000 PLC to Fernhill SCADA these steps are required:

Obtain a connection cable and connect the MicroLogix 1000 PLC to a Windows computer running RSLogix 500.
Configure the MicroLogix 1000 PLC using RSLogix 500.
Configure Fernhill SCADA.

Connection Cables

The MicroLogix 1000 PLC can connect directly to a serial port on a PC. The serial port on a PC is usually a 9 pin D-subminiature connector. These cables are suitable to connect the PLC to a computer with a 9 pin D-subminiature connector:

1761-CBL-AP00: 0.5 m length
1761-CBL-PM02: 2 m length
1761-CBL-PM05: 5 m length
1761-CBL-PM10: 10 m length

As an alternative you can create your own cable using this wiring:

MicroLogix 1000		PC
GND	2	5	GND
RTS	3	8	CTS
RXD	4	3	TXD
DCD	5	1
CTS	6	7	RTS
TXD	7	2	RXD
		4 + 6	DTR + DSR

Note: All other pins not shown in the above diagram have no connection.

Configuring the MicroLogix 1000 Serial Port using RSLogix 500

You can use RSLogix 500 to configure the MicroLogix 1000 Serial Port.

Open a project in RSLogix 500 and in the Project window select Channel Configuration:
Double-click the Channel Configuration branch to open the DF1/485 Configuration window:

Note: Choose DF1 as the primary protocol. Fernhill SCADA does not currently support DH485.
Click OK to save the configuration. If you have changed the configuration away from the defaults, you may receive a warning about loss of communication. Ignore the warning and, after communication is lost, change the configuration of the AB_DF1 device in RSLinx to match.
If you lose communication after changing both the configuration of the PLC and RSLinx, you can recover using this procedure:
1. Obtain a 1747-UIC (USB to DH-485 Interface Converter).
2. Plug the 1747-UIC into the Computer running RSLinx
3. Install the 1747-UIC following the instructions in the manual 1747-IN063.
4. Connect the 1747-UIC to the MicroLogix 1000 using a 1761-CBL-PM02 cable (or similar).
  Note: When the MicroLogix 1000 detects a communication failure on the serial port, it will switch between DF1 and DH485 protocols. The MicroLogix 1000 continues to switch until communication is re-established. The 1747-UIC should re-establish communications with the MicroLogix 1000 using DH485.
5. Change the configuration of the MicroLogix 1000 serial port using RSLogix 500.

Configure Fernhill SCADA

There are two methods to configure Fernhill SCADA to communicate with a MicroLogix 1000 PLC:

The easiest way is to use an autodetect wizard. The wizard will try different settings to work out the correct Fernhill SCADA configuration. Use one of these wizards depending whether the PLC was configured to use Full Duplex or Half Duplex Slave:
- Allen Bradley DF1 Full Duplex Autodetect Wizard
- Allen Bradley DF1 Half Duplex Autodetect Wizard
Manually configure Fernhill SCADA to match the configuration of Channel 0 of the MicroLogix 1000 PLC.

Manual Configuration

The default communication settings for the MicroLogix 1000 are:

Parameter	Value
Baud Rate	9600
Protocol	DF1 Full Duplex
Error Check	CRC
Node Address	1

The Fernhill SCADA configuration that corresponds to these defaults is:

Allen Bradley Serial Port
	Mode	Baud=9600 Parity=N Data=8 Stop=1
	Protocol	DF1 Full Duplex
	ErrorCheck	CRC
Allen Bradley PLC
	Destination Node	1

Further Information

Allen Bradley serial channel

For information about Allen Bradley serial channel configuration.

Allen Bradley PLC

For information about Allen Bradley PLC Tag configuration.

Serial Communications

For background information on serial communications.

Allen Bradley Driver

For information about the Allen Bradley Driver.

Glossary

For the meaning of terms used in Fernhill SCADA.