Opening Legacy Omron *.onw, *.swb, *.swp Files in CX-One

Overview

Three legacy Omron file extensions regularly appear when a maintenance engineer opens a twenty-year-old control cabinet: *.onw, *.swb, and *.swp. None of them can be opened by double-clicking inside a modern CX-One installation, and the error message CX-Programmer or CX-Designer returns is typically generic ("Cannot open file" or "Unsupported format"). This reference identifies each file type, names the legacy authoring tool that produced it, and gives the exact import path into CX-One (CX-Programmer, CX-Designer, and the separate NT-Series Support Tool installer).

The target audience is a controls engineer who has inherited an Omron C-series or CV-series PLC with an NT-series HMI and needs to recover, view, edit, or migrate the application. The procedures below cover SYSMAC SYSWIN 3.x ladder project recovery, NT31/NT61 screen project recovery, and the practical migration path from the discontinued NT31C/NT61C terminals to current NS-series hardware using CX-Designer.

Legacy Omron File Format Identification

Before attempting any import, confirm what each file actually contains. A control cabinet often contains all three extensions at once because the integrator kept the PLC logic (SYSWIN), the HMI screen (NTST), and a periodic backup (SYSWIN .swb) on the same archive disk.

Prerequisites

• CX-One v3.1 or later installed (v4.x recommended). The bundled CX-Programmer must be version 6.1 or later to import SYSWIN 3.x projects. Verify under Help → About CX-Programmer; older CX-Programmer builds only list "OMRON SYSMAC-C (*.cpr)" in the file-type selector.
• Local administrator rights on the engineering workstation. Both the NT-Series Support Tool installer and SYSWIN 3.x legacy installer write to %ProgramFiles%\Common Files\Omron.
• A copy of the original files in a working folder such as C:\OMRON_RECOVERY\. Never operate on the live archive copy until the import has been verified.
• For NT-screen migration: a licensed or trial installation of CX-Designer v3.x (bundled with CX-One v4.x).
• NT-Series Support Tool media (CD or downloaded installer). The utility is no longer bundled with CX-One as of v4.0 but is still distributed as a standalone installer; confirm availability with your Omron regional representative.

Opening *.swp SYSWIN 3.x Projects in CX-Programmer

SYSWIN 3.x was the DOS/Windows authoring tool for the C200H, C200HS, C200HX/HG/HE, CQM1, CPM1, CPM2*, and CV-series PLCs. The *.swp archive contains a compressed ladder program, I/O comment table, and (optionally) symbol table. CX-Programmer reads the file directly, performs an internal symbol translation, and offers to save the project in the modern *.cpr format.

1. Launch CX-Programmer.
2. From the menu bar select File → Open (or press Ctrl+O).
3. In the Look in dropdown, navigate to the folder containing the *.swp file.
4. Click the Files of type dropdown (default value is "OMRON SYSMAC-C Files (*.cpr)") and select SYSWIN 3.x Project (*.SWP). Selecting the wrong type causes the file to appear greyed-out in the list.
5. Select the file and click Open.
6. When the Device Type prompt appears, confirm the target PLC family (e.g., C200HX, CPM2C, CQM1H). Mismatching the device type will produce an "Address out of range" error when the program is later transferred.
7. CX-Programmer displays a conversion report listing any unsupported instructions. Most SYSWIN 3.x ladder elements import cleanly; documented exceptions include the older SCAL/SCL2 SCL2/3 operands and certain CV-series function-block constructs.
8. Immediately save the project as *.cpr using File → Save As. Choose a modern device type in the save dialog so that later upgrades to a CJ2 or CP1 series remain possible.

Recovering *.swb SYSWIN Backup Files

The *.swb extension is SYSWIN's automatic backup file, generated whenever a *.swp is saved. The backup contains the same ladder payload but uses a different header so that the file dialog does not surface it by default.

1. Open Windows Explorer and navigate to the folder containing the *.swb file.
2. Right-click the file and choose Rename. Change the extension from .swb to .swp. Windows warns about changing the extension; click Yes.
3. Follow the procedure in the previous section to open the renamed file in CX-Programmer.

If multiple generations of *.swb files exist with timestamps, open the most recent one first. SYSWIN only keeps one backup per save, so an older *.swb may represent the last working revision before a problematic edit. Always diff the two imports before committing to one.

Opening *.onw NT-Series Screen Files

An *.onw file is a screen project for an NT-series Programmable Terminal: NT20, NT30, NT31, NT31C, NT600, NT620, NT610G, or NT61C. The file was produced by the NT-Series Support Tool (NTST), a 16-bit Windows utility that was discontinued when Omron introduced the NS-series PTs in the early 2000s.

CX-One cannot open *.onw files directly. CX-Designer can only open NS-series *.ism projects. Two recovery paths are available:

Path A: Install the Standalone NT-Series Support Tool

1. Obtain the NT-Series Support Tool installer from your Omron representative. Confirm you receive the version that matches your PT model: NTST-V2 (for monochrome NT20/30/31) or NTST-V3 (for the NT31C/NT61C color terminals and the NT610/620).
2. Install the tool in a dedicated folder such as C:\OMRON\NTST\. Do not install it under Program Files (x86) on Windows 10/11 without enabling NTST's compatibility shim; the installer assumes writable registry keys and a short path.
3. Launch NTST, then File → Open and select the *.onw file. The tool reconstructs all screens, alarm tables, and the PT-to-PLC tag table.
4. Export to a usable archive using File → Save As. Save to the same *.onw name in a working folder.

Path B: Migrate to NS-Series Hardware

If the NT31C or NT61C terminal is failing or has been discontinued by your spares policy, Omron's official migration path is to convert the *.onw project to a CX-Designer NS project and upload it to a current NS5/NS8/NS10/NS12/NS15 PT.

1. Launch CX-Designer from the CX-One installation.
2. From File → New Project, select the target NS-series PT model (NS5-SQ10-V2, NS8-TV01-V2, NS10-TV01-V2, NS12-TS01-V2, NS15-TX01S-V2 are common modern equivalents).
3. Recreate the screens manually using CX-Designer's component library. The screen resolution, color depth, and touch-cell grid differ between NT and NS hardware, so a 1:1 pixel conversion is not possible. Use the original *.onw project (opened in NTST) as the reference for text labels, switch addresses, and alarm messages.
4. Re-bind every PT switch and lamp to a PLC address. NT-series terminals used NT Link 1:N (Host Link over RS-232C/RS-422) with a configurable unit number; NS-series terminals default to Ethernet/IP or serial Host Link, and the polling group table must be rebuilt.
5. Compile the project (Project → Compile) and resolve any "Unused tag" warnings. NS terminals use a strict tag database; the implicit tag creation used by NTST is not preserved.
6. Transfer the project to the NS PT via USB or Ethernet, then verify every screen against the original NT screens on the bench before installing in the field.

SYSWIN to CX-Programmer Instruction Compatibility Matrix

Not every SYSWIN 3.x instruction survives the round-trip into CX-Programmer. The table below lists the most common instruction-level conversions an engineer will encounter on a C-series recovery job.

Conversion Limitations and Compatibility Matrix

Verification Procedures

After every legacy import, perform the following verification before connecting to a live PLC. Each step takes seconds; collectively they prevent the most common recovery errors.

1. Cross-reference I/O comments: Open the imported project in CX-Programmer and confirm that the comment table contains meaningful text. An empty comment table usually means the wrong device type was selected during import.
2. Cycle the program offline: Use Program → Online → Work Online Simulator (CX-Programmer v7.x and later). Step through the first ten rungs to confirm instruction order and operand addressing.
3. Compare against the cabinet label set: If the cabinet has a laminated I/O list, verify the IR/SR addresses match. Mismatches indicate the wrong *.swp generation was imported.
4. Validate the PLC clock and DM area: Read DM0..DM99 in Monitor mode. The original DM values from the on-line PLC should match the imported defaults; differences indicate corrupted file save.
5. Test communications: Connect via the original peripheral port or RS-232C and perform an Upload (read from PLC). The upload should match the imported file. Any difference means the imported file is stale.
6. For PT migration: With CX-Designer in offline simulation mode, click through every screen and confirm each switch, lamp, and alarm trigger. NS-series terminals do not gracefully render broken tag references.

Field-Commissioning Notes

• Communication port quirks: SYSWIN 3.x default Host Link baud rate was 9,600 bps with unit number 00. Many legacy C-series PLCs are still configured this way. When CX-Programmer fails to auto-detect, manually set the baud rate and unit number in PLC → Auto Online → Direct Online.
• Battery-backed DM: C200H, C200HX, and CV-series retain DM and HR areas on power-down. Always perform an Upload (read from PLC) before any Online Edit. A corrupted *.swp that overwrites the on-line DM with all zeros is unrecoverable without the original transfer tool.
• Memory cassette workflow: If the C-series CPU uses an EEPROM memory cassette, save the recovered program to the cassette using PLC → Transfer → To Memory Cassette. The cassette acts as a long-term backup that survives battery failure.
• NT31C/NT61C lamps: NT-series lamp control words use BCD-packed bits. When migrating to NS-series, the equivalent function is the multi-state lamp component, but the bit-to-state mapping must be re-declared in CX-Designer.
• Sysmac Studio consideration: As of CX-One v4.5, the modern authoring environment for CJ2/CS1/CP1/NX/NJ families is Sysmac Studio. A *.cpr file saved from a SYSWIN import can be opened in Sysmac Studio via File → Open → Import CX-Programmer Project; expect to re-enter the device type and network topology.

Error Code Quick Reference

FAQ