Mitsubishi PLC FX3U

Hi, I have FX3U PLC from an OEM, I am trying to get the original program out of the PLC using GX works 2.

While uploading I am getting an error staying the program might be programmed using structured text or FB, due to which the uploaded program will be different than the original program.

I called Mitsubishi support and the guy said to be able to upload the program with structure text and FB I need an original code from the OEM.

Support said I can download the uploaded program(in ladder form) from the PLC without making any changes and it will work the same(can be used only as a backup).

Questions:

1. Is there a way I can upload the program in the original format?
2. If I have a program that got converted to ladder logic while uploading, can I safely make changes to this program and download those changes?


I am trying to make changes to the existing PLC program.

I have attached the uploaded file.





Thank you!

Most likely you can't upload in original format, as symbolic data was not download to PLC.
Also there is no attachment.

Here is the uploaded program.

The other OP's are correct, unless the original programmer downloaded the symbolic table it cannot be re-constructed, also, is this originally a GXWorks file or the older GXIEC, I have noticed some errors when open (highlighted in yellow), this means it does not conform to normal operation and it may be it will not download, I have seen this when GXIEC developer was used, it sometimes creates code that appears not to be compatible but works.
So the only way to get back to structured project is to contact the original supplier & see if they will give you the file or re-construct it by manually doing it but this is not easy by any means and easy to make mistakes.

The bit that came up highlighted in yellow I have solved, I changed the M8000 that enabled the rung then changed it back & it re-compiled so should be ok.
The way that GXWorks2 works is that it uses jumps to pointers so a lot of the code is actually outside of the normal main scan, these are the different structured blocks or function blocks. i.e.
MAIN.

A xxxx // if true then
CJ P2048 // conditional jump to pointer
..... // more code in main scan
.....
FEND // End of main scan

P2048 A xxxxx // This is the pointer to the code
.......
........
RET // Return from sub routine

END // end of code
So in reality it is one long bit of code but it uses conditional or un conditional jumps to the various blocks and returns to the main ladder.
Attached is the one I re-compiled.
I also suggest you upload to your file the PLC parameters & the Device memory as these could be different from your file, also in the device memory it will take a snapshot of the data held so if you need to replace the PLC it will have any data that is fixed or held in the memory. do this when the machine is not running i.e. idle.


........

Parky,
First and for most thanks for replying, I tried to upload by Select All and it gave me any error that my device name is empty I am not sure how to fix that.
I was able to upload the program when I selected the Parameter+Program option instead of Select All.

The file that you have given me, if in case of having to replace the PLC can I download this program and it will work the same(just confirming)?

Editing this program will be tough for sure as I do not have a tag/comment list. The manufacturer has kept the comment memory "0"(No comments at all).

You may have to create it in the tree on the left hand side there is Device memory
Right click and add New Data, the default is MAIN, then try to upload the device memory from the PLC, it will take a snapshot of the device memory then save the file, You should be able to add some symbols if you have some drawings at least for the I/O. I think you need to keep the original, I have a feeling that the one I sent you will have some bits missing, I have noticed that on some ladders they use M8000 which is the always true bit to poke values into registers, GXWorks allows as many branches as you wish but GXDeveloper does not so I think it deletes them, so do not use the one I sent you, tomorrow I will load the original to an FX3 & do some mods to the file by adding extra M8000 however, I do not know at this point if it will delete any I can check by comparison.

If you look at the original upload you did at 4070 you will see this as being in yellow, that's because the GXWorks (In GX Dev Ladder mode) does not like how it is in the compiled code, there will be some nops that you cannot see, this is because there has probably been some on-line changes difficult to explain but when on-line changes have been done in the past in pushes some nops in the code and shifts the program (the editor ignores them). When I changed the the m8000 to something else then back again it compiled but removed the nops so the code when verified with the original code seems different in two places, the code is actually the same but the original uploaded contains a block of nops. that do not display so as there are address spaces different between the original & modified it sees them as if the code is missing.
If you run two sessions of GXDEV one with the original program & one with the modified (suffixed with "1" on the file name, and scan through both you will see no differences except for the line numbers go out of sync at the re-compile i.e. where the yellow block is shown. but the whole code is the same, so although it says it is different it is the same, I have looked though both programs & there are no differences.
So I have attached the modified one for you to check.
You will find that editing in some areas will be impossible to do it on-line, you will have to modify it & download, as it uses a lot of conditional jumps only small changes can be made & some of the sub routines are pretty large so can only be done off-line then the whole program downloaded.

Hello, Good day. Can someone help how to buy a GX developer software(Mitsubishi) and a data cable FX3U RS232-USB cable?
I have tried to email Mitsubishi sales team but they didn't revert.

I want to connect to MELSEC FX3u, do I need the backup from machine supplier as we do with SIMATIC7 ???

I don't know what would be involved with shipping from the US, but you could try this.

drbitboy said:

I don't know what would be involved with shipping from the US, but you could try this.

Click to expand...

I appreciate.

I suggest you start a new thread as this one is something different, however, things you need to be aware of.
It depends in what IDE the original was programmed in for example:
If in GXDeveloper then either GXDeveloper or GXWorks2 (GXW2 actually also contains a compatible mode of GXDev)
If in GXIEC or GXWorks2 then again depending on what language they used if pure ladder then GXDeveloper or Works is fine.
The problem is as shown in the above posts if done in FBD or structured project (GXIEC or Works) then the code returned will be in a sort of ladder with lots of CJ jumps to subroutines using many bits/words in the 7000 range (this is how the IEC is used to make it compatible with ladder/IL).
Also if someone has password protected the PLC then you will need the password or you cannot upload the code.
There is a FX only version (or was at a reasonable cost but I do not think is is now available) but RS do the GXWorks2 but not cheap.
It is possible that the original programmer downloaded the symbolic table that will re-construct the project in GXWorks2, however, that is unlikely as many do not bother or if the program is moderate to complex there will not be enough spare memory to store it.