Off-line Programming?

Hello, I'm studying PLC's at college and need to know what Off-line programming is and what are it advantages and disadvantages.

Can anybody give me an answer to help me on my way?

Thanks guys!

Offline programming is where most of the programming work is done, say at your desk. The software is not connected to the PLC processor. After you're done with the bulk of the work, you can download it to the processor and certain processors will allow you to program will you're connected live to the machine.

Online programming allows you to edit, add, and delete while the program is running.

Thanks buddy!!

Robert

The main issue about online and offline programming is that with PLCs the device that executes the program is not the same as the one on which the program is created. This is unlike PCs where, for example, you write a Java or C application and then execute the application on the same machine.

With PLCs you usually use a PC to create the program and the PLC then executes it. If you do this while connected live to the PLC you are doing online programming. If you create the code away from the PLC and then download it at a later stage, you have been doing offline programming.

Simple as that.

Advantages and disadvantages? Thousands. Depends what you want. Immediate access, seeing your changes take place on the fly, getting an immediate response from things you've done? Go online. Don't want to be anchored at the end of cable in a cabinet beside a noisy, smelly machine somewhere? Go home and do it offline. Most PLCs don't have the ability to store any documentation for the program in their memory (I know Siemens S7-400's do) so any comments etc must be stored offline. No doubt others will chip in with ideas ...

Regards

ken.

Most PLCs allow online editing of the program. This means editing the logic while the machine is actually running. The advantages are that you can see the effects if your changes immediately, and you don't have to stop the machine that's being controlled. It is usually only used for minor enhancements. I find myself doing some major changes online for the fact that it doesn't stop production. The disadvantage to online editing is that if you make a mistake, the results can be detrimental, and even dangerous to the machine operation. Offline programming refers to writing/editing logic with a PC that isn't "online" with a PLC. Starting a new program from scratch is usually done offline. Some configuration changes to a PLC must be done offline. Once the program is written, it is then downloaded to the PLC. Offline editing is usually faster, and definitely safer, but the disadvantages include:
1. When you're ready to download, the PLC processor must be stopped to download the changes.
2. It's easy to accidently delete lines of ladder logic (RSLogix).
My experience is limited to Reliance/Allen-Bradley PLCs...Hope this helps.

Most PLCs don't have the ability to store any documentation for the program in their memory (I know Siemens S7-400's do)

Click to expand...

So do the newer S7-300s if youput a big enough MMC in them.