Delta Electronics ships two programming tools — the legacy WPLSoft and the current IEC 61131-3 IDE, ISPSoft. Here is what each one is, how they differ on languages and PLC series, and when it makes sense to migrate an existing DVP project.
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Quick answer
ISPSoft is Delta’s current programming software; WPLSoft is the legacy tool. ISPSoft follows the IEC 61131-3 standard — ladder, structured text, FBD, SFC and IL, organised into a proper multi-POU project — and covers the DVP, AS and AH families. WPLSoft is Delta-style ladder, instruction list and SFC only, built mainly for the DVP compact series. Both are free and both are Windows-only. New projects should start in ISPSoft; WPLSoft remains relevant for maintaining older DVP machines whose programs were written in it.
The two tools
WPLSoft is Delta’s older programming software, developed in the era when the DVP compact series was Delta’s flagship PLC line. It programs in Delta-style ladder diagram, instruction list, and SFC, using the classic DVP device addressing (X inputs, Y outputs, M relays, D registers).
Its strength is simplicity: a small install, a flat program structure, and a directness that suits quick edits on small machines. Its weakness is everything the IEC 61131-3 era brought — no structured text, no function block diagram, and no modern project organisation. Delta’s newer controller families are not the target; WPLSoft is a DVP-era tool.
ISPSoft is Delta’s IEC 61131-3 programming environment, covering the DVP, AS and AH PLC families. It supports ladder, structured text, FBD, SFC and instruction list, and organises code the IEC way: a project of POUs (program organisation units), function blocks, global and local variable tables, and symbolic addressing alongside the raw device addresses.
That structure is the real upgrade. Reusable function blocks, typed variables and multi-POU projects are how modern automation code is written on every major platform — Siemens, Codesys, Allen-Bradley — so time in ISPSoft builds transferable habits, not just Delta-specific ones. (Delta has since introduced DIAStudio for its newest series, but ISPSoft remains the standard tool across the DVP/AS/AH installed base.)
Side-by-side
| Feature | WPLSoft | ISPSoft |
|---|---|---|
| Status | Legacy — maintained for older projects | Current standard Delta IDE |
| Supported PLC series | DVP compact series (its home turf) | DVP, AS and AH families |
| Ladder diagram (LD) | Yes — Delta-style ladder | Yes — IEC 61131-3 ladder |
| Instruction list (IL) | Yes | Yes |
| SFC | Yes | Yes |
| Structured text (ST) | No | Yes |
| Function block diagram (FBD) | No | Yes |
| Project structure | Flat, single-program style | IEC multi-POU: programs, function blocks, variable tables |
| Simulation | Ladder simulation (via COMMGR) | Simulator mode (via COMMGR) |
| Operating system | Windows only | Windows only |
| Price | Free | Free |
Both tools are free downloads from Delta Electronics’ official site. If you are unsure where to download vendor software safely, see our PLC software download guide.
Migration
The most common real-world question is not “which is better” — it is “I have a plant full of DVP machines programmed in WPLSoft; do I move them?” The honest answer is: only when there is a reason to.
ISPSoft can import WPLSoft projects, which does the heavy lifting — but treat the import as a starting point, not a finished migration. Review the converted logic rung by rung, check that comments and element labels survived, and re-run the program in simulation before downloading to a production PLC. Device addressing (X/Y/M/D) carries over, but the surrounding project structure changes, so anything that referenced the old flat layout — documentation, backup procedures, change logs — needs updating too.
For brand-new projects there is no debate: start in ISPSoft. You get the full IEC 61131-3 language set, a project structure that scales past one machine, coverage of Delta’s current controller families, and skills that transfer to every other IEC-based platform.
Before the install
Whichever Delta tool you land on, the hard part is the same: reading a rung, building seal-in logic, driving timers and counters, and thinking in the scan cycle. None of that requires a Windows VM or a COMMGR driver. You can drill exactly those fundamentals in a browser-based Delta-style PLC simulator on any OS — including the Mac that ISPSoft will not run on — then move into ISPSoft once the concepts click.
The simulator is a learning environment, not Delta’s software: it does not compile to DVP firmware or upload to hardware. What it does is give you scored, auto-graded ladder practice with zero setup, so your first hour in ISPSoft is spent on Delta specifics instead of on “what is a normally-closed contact”.
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