PLC5 Prevent Download Overwrite

Processor AB PLC5/40

I have a PLC5 processor that is used to control a number of equipment such as roller mills etc. There are a few totalizers as well as equipment runtime meters etc. The data is stored as float and/or integer in assigned data tables.

If an offline upgrade was done to the equipment the programmer would have to record all the above data then download and update the relevant tables as they would have been replaced by the offline file. An error took place were I believe a program was downloaded into the processor and set all the values back two weeks (time of last upload).

I was wondering what would be the method(s) others have used to deal with this sort of issue, as well if there was someway of selecting some data tables to be write protected by program download.

This is the main reason I very rarely download to a running system. Most changes are made with online edits. If you have to make a change that requires a download (like adding a new data table) the procedure is:

Shut down the process.
Put the processor in program mode.
Upload the program.
Make the changes.
Download the program.

Mellis has it absolutely right and its the golden rule in my book for any plc mfg.

I fully agree with Mellis as well.

That situation where the data was changed occurred, and from my investigation the only reason I could think of was a program download. There was no report of a problem so I believe that there was some issue that resulted in a program download maybe an error by the technician troubleshooting.

For this reason I was rather interested in the idea of masking a particular data file from program download somehow if it is even possible.

It has been many years since I regularly worked with the PLC-5, but I believe that there was at least limited support for partial downloads. That could achieve masking out the data file as you mentioned.

Also, it is possible to mark a data file as static, preventing it from being modified by a communication channel. I am not sure if that would be overruled by a download.

You may want to investigate the above possibilities, but if they're proven not to be effective, then fall back on the wise suggestions by Mellis.

Paul

It's actually very simple to do using AB6200. Upload your project to your laptop, go off to your office to make your changes, and save the program as a .PC5 file (export it to .PC5 format).

Now pick a time when the machine will be available, and upload the current program from the machine. Save that as a .PC5 file as well (under a different name of course).

Open up notepad in Windows and look at your office file. You'll see that it's broken up into thirds. You will see the status table stuff first, your program, and then the data tables.

Chop your program part out of the freshly uploaded copy from the machine (you won't want to use it), and paste the program portion from your office copy into that space.

This way you will have your new program merged with your current data tables.

Save and close the file, and import it back in as a native AB program.

Download this to your machine, check it out carefully, and you should be good to go.


BTW, none of this is theoretical. For the conveyor systems that I wrote PLC code for the GM plant in Wentzville, MO (a dozen or so), I created a program that would develop my PLC code for me using standard schemes that we used for stops, slow-to-fast transfers, fast-to-slow transfers, bias banks, etc.

My program would build the station file from a scheme including the documentation and all internal bits automatically. All that I would have to provide was the I/O for that station.

My program would create .PC5 files for each of the stops and such, and then I would use a second program to stitch all of the stations together and sandwich it between the status and data table portions of a template (the template being what type of PLC5 that I wanted to use for that system. e.g. 5/20, 5/40, etc...)

I would then import it back into the AB 6200 software and then download it into the PLC.

It worked extremely well, and our debug time was cut to next to nothing (each scheme was thoroughly tested before it became part of the standard schemes that way I was sure that the code was going to work correctly).

rootboy, what about the data table changes that occurred between the time you uploaded and then downloaded later?

Many of todays PLC packages allow you to import pieces of logic previously exported so that you can combine new code into existing code or open two instances of a package and copy & paste with no lose of data table. Gotta love windoze.

wow, 6200, I haven't seen that since the early 90s along with Topdoc, Updoc, & OS2 .

jstolaruk said:

rootboy, what about the data table changes that occurred between the time you uploaded and then downloaded later?

Click to expand...

Well, you would upload the program the first time, take it to your office, make your changes, and then export it to a .PC5 format.

Then you would go on down to the floor, put the machine in cycle hold, and upload the floor copy. Export that to .PC5 format as well.

Take the PLC program chunk out of the floor copy and it replace it with the new PLC program chunk from your office copy.

Import this into AB6200, and download it to your PLC. Now you will have your new "offline" code merged with your current online data.

jstolaruk said:

Many of todays PLC packages allow you to import pieces of logic previously exported so that you can combine new code into existing code or open two instances of a package and copy & paste with no lose of data table. Gotta love windoze.

wow, 6200, I haven't seen that since the early 90s along with Topdoc, Updoc, & OS2 .

Click to expand...

Well, it was back in '94.

Now, I haven't used 6200 for ages, and I gave away my 5/40 years ago. So I haven't fiddled with '5's for quite awhile either. Actually, it's been Logix 5k's, MicroLogix's, SLC's, and GE 90-30's for the most part lately.


BTW, GE Series Sixes were allowing the option of downloading just your PLC code and not overwriting the data tables since the '80's.

Offtopic: I just bought a AutomationDirect Click PLC for a project here at work. I am really looking forward to trying it out. I'll post my thoughts on it after I play with it for awhile.

RSLogix5 does have a partial download feature, I have never used it so you might want to read the online help file to see if it will help you.

See picture below

Mickey said:

RSLogix5 does have a partial download feature, I have never used it so you might want to read the online help file to see if it will help you.

See picture below

Click to expand...

That would have been a nice feature for RSL500 & RSL5K to inherit.