Connecting to an Allen-Bradley SLC and Going Online

I get a lot of questions about going online with a PLC. Here is a section from PLC Programming with RSLogix 500 that covers going online with an SLC 5/03.

You have written your program and now you are ready to download, or send, the Batching program to the computer.


There are dangerous voltages present on terminals of the PLC. Follow all warnings and instructions from the Allen-Bradley manual for connecting power to the PLC. If you are not familiar with hazards and the potential dangers of these voltages STOP RIGHT NOW. Consult a trained professional who is able to assist you.

First, backup up your original file and put it in a safe place.

Check the serial port settings of your computer in Control Panel. Make sure the baud rate (or bits per second) of your COM port is set as high as possible 57600 should work there.

Allen-Bradley provides a cable to connect the serial port of your computer to the 9-pin serial port on the SLC 500 processor. Connect the cable and turn power on to the PLC.

Turn the key operated switch on the processor to the center position PROG (program).

If you do not have RSLinx installed, you will have to do that now.

After you install RSLinx, you will have to configure it for your computer and your PLC.

To do that,

Start > Programs > Rockwell Software > RSLinx > RSLinx

In the Notification are of your Taskbar (the lower right of your Windows screen) that looks like this.


The one on the left is the RSLinx Communications Service. The other one is for the RSI Directory Service.

Click on the left one, the RSLinx Communications Service. The RSLinx screen will appear.



Communications > Configure Drivers

The driver screen appears.


Choose RS-232 DF1 devices from the “Available Driver Types” drop-down menu.

Click “Add New”.


Click “OK”.


You probably have your cable connected to COM1 of your computer. Click “Auto-Configure”.

In the box to the right of the “Auto-Configure” button, you should see a message that says “Auto Configuration Successful”. In addition, the “Device:” box should show “SLC-CH0/Micro/PanelView”.


Click “OK”. You should see a screen like this.


Click “Close”. You may close the RSLinx screen – RSLinx will still run, as indicated by the icon in the Notification area of your taskbar.

Open RSLogix.

Choose Comms > System Comm… from the menu. You will see a screen like this. You may have to maximize the screen and resize the panels to get the right view.


In the explorer panel on the left, click on the “+” next to “AB_DF1-1, DH-485”. You should see animation in the icon, as the tiny blue square moves around the little network symbol. The computer icon for address 00 indicates your computer. The icon for address 01 indicated the PLC. In our case, it is an SLC-5/03.


Select the SLC in the left window and click “OK”. The communications window will close.

In the RSLogix 500 main screen, choose File. Select your program from the Recent File List (it is probably 1).

Choose “Controller Properties” from the Project tree. Click on the “Controller Communications” tab.


Click on the “Driver” dropdown box and select “AB_DF-1-1”.


Click “Apply” then “OK”.

Choose Comms > Download

You should get a screen similar to this.


Choose “Yes”.

The program will begin downloading.


Since we are downloading a new configuration, this screen will appear.


Choose “Apply”. The program is now in the PLC.

Sometimes it is necessary to cycle power on your computer. Making the first connection to a PLC can be tricky. Prepare yourself by having the phone number for your Rockwell rep handy.

If things go well, you may be able to go online right away.

Choose Comms > Go Online


Choose “Browse” and find the folder where you file is located. Click “OK”.

The file name will show in the bottom box. Click on it to select it, then click “Upload Use File”.


You may need to change the Baud Rate of the PLC. Click “Channel Configuration” in the Project tree and click on the “Chan. 0 – System” tab. Choose “19200” from the Baud dropdown menu. Click “Apply” and “OK”.


Tip: In Allen-Bradley PLC vernacular, upload means get the program from the PLC and load it in RSLogix on your computer.

Download means send the program from RSLogix on your computer to the PLC.

You will now see a screen like this. Notice that the ladder icon is animated to indicate you are online.


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