GE90-70 LM90 application help

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Hi All,

I recently had an opportunity to visit a plant that was running GE90-70 redundant PLCs with Genius RIOs communication to CImiplicity SCADA. I initially thought that the Application was done in PME 7.0 and was able to use the serial cable and upload the project using PME software. The program uploaded with no comments. However, when i went to get the backup of the SCADA program, I saw that the previous engineer made back ups of both the SCADA and PLC. When i looked at the PLC files, It struck me that the PLC application was made in LM90. I had the LM90 master software and was able to open the files using a few youtube videos as a guide. The client has asked me add a few PID loops.

I have a few questions:

1. If the PLC was loaded with LM90, how was i able to  upload the program with PME?.

         1a. If so, can I make online changes with PME to add the 3 PID loops without going back to LM90

2. If 1a option is not possible, I would have to use LM90 to make the changes. does LM90allow online changes?

LM90: Questions

I have plenty experience with PME, but this would be my first time with LM90. Before going to a site i would like test the process of upload, download in my office. So i have few queries about this software:

1. I am able to get hands on GE 90-70 PLC that was programmed with PME. Will i be able to create new application with few logic in LM90 and download to this PLC and test the whole process of testing my logic and upload/download procedure. And when once i am done, load the PME application back into it. I am not sure if I would have downgrade the firmware of the PLC?

2. , Does LM90 have option to make offline changes and download only changes, if so will it stop the PLC when downloading?.

I would appreciate all the help in this matter


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Welcome to @suraj  .  I hope our GE Users can answer your question.

I touched one GE System 19 years ago, but it was 90-30 and I had an experienced engineer at the time to provide me hands on training.


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Once a program has been modified using PME, it can no longer be opened with LM90. But the PLC itself doesn't care what program you employed to create the program you want to download to it.

In answer to question 1, PME can recognize and upload a LM90 program. LM90, being older software can't recognize a PME program.

In answer to question 1a, you will find that after uploading a LM90 program using PME, you will be in a "Logic not Equal" state. Thus, you won't be able to make online changes without first downloading what you just uploaded.

In answer to question 3, LM90 permits online changes.

In answer to LM90 question 1, yes to both downloading a LM90 program to a PLC previously programmed using PME and to later downloading the PME program to the same PLC. I doubt if the firmware will be an issue, but I can't give you any guarantee.

In answer to LM90 question 2, you can generally download program changes to a 90-70 without stopping it. The way LM90 does online changes, it will download the only the modified program blocks to available free memory and then change the starting address of the subroutines. Doing this enough times eventually creates fragmented memory. If there is not a large enough block of free memory to accommodate the modified program blocks, the online change won't be possible. In that case you would have to stop the program before downloading.

Having said all that, the fact that you have a redundant system complicates things. GE offered multiple redundancy strategies over the years.. Some of them included proprietary program blocks along with the ladder logic specific to the application. Your best bet is to get the manuals for your particular redundancy strategy and familiarize yourself with the procedures for making modifications and for downloading those modifications to both CPUs.

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I'm not sure if this is still possible, but PME offers (offered?) an import option for LM90 files so you'd pick up the comments.  I used in some years ago.  You might want to look at that option.  You'll still have to do one full-stop download to achieve Logic Equal after switching tools.  After that run-mode-store will be available for online changes.

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@suraj it sounds like @Steve Bailey and @pturmel have started you in a good direction.

Please post back the final resolution and any intermediate issue, so others that might encounter your issue can learn from you.

Welcome again to

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Thank you @Steve Bailey for replying here and in other forums. I will continue in this forum. 

@pturmel  This is fairly large system with Redundant Controllers. So far the Client has requested to just add a couple of loops and we proposed for a couple of days to do this onsite with SCADA update. I am not sure of all the risk involved in changing it to PME and performing a download for a live plant and assume that it all will run smooth afterwards including Setpoints, Sequence states and forces and redundancy functionality and for me to test all operations within 2 days.

So that why wanted to keep the risk to the minimal when on site. 

@BobLfoot I will keep posted on what i have done to solve this issue so that it can benefit others. I will be getting GE90-70 PLC rack next week and i will test on it first using LC90 software and see how it goes and then go to the plant to go online using the backup that was last saved and make sure i have clean project with HW and Logic equal and test a small logic change onsite. Once i am confident and i will make these online changes for the new PID loops 

Thank you again for all the help

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I was able to go to site and use a copy of the programing that the customer had. I saved the program under LM90 directory and was able to use LM90 software and open the program and then went online with the PLC. I did see that the logic was not equal and i performed load from the PLC to PC.

However, This is a redundant system so the customer had 2 file for each of the PLC L2PLC01 (primary) and L2PLC02 (secondary). Again Under LM90\L2PLC01 file folder, there was a file for L2PLC02 also which confused me. However under LM90\L2PLC02 there was no folder for L2PLC01.

So when i reached the site, I saw that the L2PLC01 was secondary and L2PLC02 was primary. I went online with L2PLC01 using the file LM90\L2PLC01. I saw that there was a mismatch for only one logic block and i went ahead did a load from PLC to PC. Then I went online with L2PLC02 PLC using the LM90\L2PLC02 file. I saw there was mismatch on several logic block. I still went ahead  did a load from PLC to PC so that i have the most currect files for both PLCs.

The scope of work is to add just one PID loop to the Logic. So I have the following questions:

1. Which PLC should i go online to make the changes (My guess is the primary PLC)

2. How do i make sure that the secondary PLC has the updated logic. DO i need to go online with secondary PLC and redo the same logic online? or is there a command to synchronise the logic from primary to secondary?

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