Compare two versions of a Mitsubishi PLC project
The program in the PLC was changed at the machine and the copy on the server is older. A contractor sends an updated project with "small changes". Two backups have different dates and nobody knows which one is running. Upload the older version as the MELSEC project and the newer one under "Second version to compare", and get a list of every difference.
What is compared
| Area | Differences listed |
|---|---|
| Project | CPU type and project title |
| Programs | programs, function blocks and functions added or removed, a new language, program file or task, and changes to the program setting |
| Logic | ladder blocks added, removed or changed (drawn before and after, with the step numbers in both versions), changed lines of structured text, and changed elements of structured ladder, FBD and SFC |
| Statements | statements and notes changed without a change to the logic |
| Device comments | comments and aliases added, removed or reworded, device by device |
| Labels | global and local labels added or removed, and changes to class, data type, device, initial value or comment |
| Structures | structures added or removed, and changed members |
| Parameters | device points, memory and comment capacity, latched ranges and the PLC name |
Ladder blocks are matched by their content, not by their step number, so a block that only moved because something was inserted above it is not reported as changed. Structured ladder and FBD networks and SFC blocks are compared as the list of their elements, steps and transitions.
The report
- PDF: a summary table of differences by area, then every difference with its program and step, changed ladder blocks drawn in both versions one above the other.
- HTML: the same report as one web page, for reading on screen.
- Excel: one row per difference with area, kind of change, program, item, before and after, for filtering and for writing up a change log.
The result page shows the number of differences by area and the first ones, before any download.
Which files can be compared
Any two of the files this tool reads: GX Works2 .gxw, GX Works3 .gx3, zipped GX Developer
projects, single .wpg program files and instruction list .csv exports. Programs are matched
by name. Both files are also read in full, so the printout, viewer and tables of the first
project come with the comparison.
Typical uses
- Find out what was changed during commissioning before archiving the final version.
- Check a contractor's update before loading it into the PLC.
- See which of two backups is newer, and by how much it differs from the other.
More about what this tool reads and writes: Mitsubishi PLC Project Viewer (GX Works2, GX Works3, GX Developer).