Problem Overview
Engineers migrating Mitsubishi HMI programming to a Windows 7 64-bit host with a Windows XP Mode (Virtual PC) guest frequently encounter a recurring fault: GT Designer 2 can talk to a MELSEC FX3G PLC over a USB-to-serial adapter, but the same adapter, cable, and virtual machine cannot establish a link to a GOT1000-series operator interface terminal (OIT). The upload dialog stalls, the transfer tool returns a timeout, or the GOT does not appear in the connected-device list at all.
This article walks through the underlying cause (virtual COM port remapping), the diagnostic procedure, the correct transfer tool configuration, and the alternate communication paths (Ethernet, USB, FA transparent) that should be used when the XP-Mode serial stack is the limiting factor.
Root Cause: COM Port Remapping in Windows XP Mode
Windows XP Mode (XPM) is a Virtual PC instance that runs as a child process of the Windows 7 host. USB-to-serial adapters are presented to the guest OS through the Virtual PC COM-port arbitrator, and the numerical COM identifier inside the guest is not guaranteed to match the COM number assigned by the host OS.
Concrete example taken from the field report:
- Windows 7 host: USB-serial adapter enumerated as
COM4. - Windows XP Mode guest: same physical adapter enumerated as
COM3(or any other free number) by the Virtual PC serial arbitrator. - GT Designer 2 was configured for
COM1(the original desktop COM port, not the USB adapter) and therefore tried to open a port that no longer existed in the guest.
The FX3G link worked because the engineer happened to set GX Developer's transfer setup to the correct guest COM number; the GOT1000 link failed because the GT Designer 2 transfer setup still pointed at the original desktop COM number.
Affected Configurations
| Layer | Component | Common Value | Risk |
|---|---|---|---|
| Host OS | Windows 7 64-bit | USB-serial on COM3/COM4 | Adapter binds here, not in guest |
| Guest OS | Windows XP Mode | COM1 reserved, USB-serial on COM5 | Numbering differs from host |
| PLC tool | GX Developer 8.103H | Configured for COM3 | Correctly re-pointed at guest port |
| HMI tool | GT Designer 2 (GOT1000) | Still configured for COM1 | Wrong port → upload failure |
| HMI platform | E1000 (e.g., E1101) | Different toolchain entirely | Cannot be reached with GT Designer 2 |
Prerequisites
- Administrative rights on both the Windows 7 host and the Windows XP Mode guest.
- USB-serial adapter with the correct Mitsubishi driver (FTDI-based devices such as USB-RS422-PCB-1 or the Mitsubishi GT09-C30USB-5P are the safest choices).
- GT Designer 2 (or GT Designer 3) installed inside the XP-Mode guest, not on the host.
- Know the GOT1000 model number (GT1575, GT1675, GT1585, GT1665, etc.) and the matching communication driver installed in the GOT project.
- The original GOT project (.GTE or equivalent) or a clear understanding of the existing GOT IP / COM / driver configuration.
Step-by-Step Resolution
1. Identify the guest COM number
- In the Windows XP Mode guest, open
Control Panel → System → Hardware → Device Manager → Ports (COM & LPT). - Locate the USB-SERIAL CH340 (or FTDI, Prolific, etc.) entry and note the COM number in parentheses, e.g.
USB-SERIAL CH340 (COM5). - Close Device Manager and open GT Designer 2.
2. Re-point the GT Designer 2 transfer setup
- In GT Designer 2 menu select
Communication → Transfer Setup(or in GT Designer 3:Online → Transfer Setup). - Set the PC side I/F to
Standard COM(orRS-232) and select the COM number that matches Device Manager — in the example above,COM5. - Set Baud rate to
115200, data length8, parityNone, stop bit1, flow controlNone. These match the GOT1000 default loader settings. - Click
Connection Test. A successful test returns "Connected to GOT".
3. Verify the GOT side communication driver
If the connection test still fails, the GOT itself may not be set to the right loader protocol. From the GOT1000 utility screen (touch the top-left corner four times within 2 seconds to open the Main Menu) navigate to Communication → Communication Parameters and confirm:
- Channel:
CH1(or whichever channel the USB-serial is wired to through the GT09-C30USB-5P cable). - Driver:
MELSEC-FX,MELSEC-Q, or the specific driver matching the connected PLC — notHost (PC)unless you intentionally want FA transparent mode. - Baud: matches the PC side (115200 is the safest default for GOT1000 loader communication).
4. Try the dedicated GOT USB loader
On GT16, GT15, and GT14 hardware the USB port on the front face is a slave port that talks directly to GT Designer. The USB-serial adapter is not required: plug a standard USB-A → USB-B (printer-style) cable between PC and the GOT's USB slave port, then in GT Designer 2 select Transfer Setup → GOT USB. This path bypasses the XPM COM arbitrator entirely and is the most reliable upload route on a Windows 7 64-bit host.
FA Transparent Mode (GOT ↔ PLC through PC)
FA transparent mode allows GT Designer 2 to read or write the connected PLC through the GOT, using a single USB or Ethernet cable from the PC. It is enabled in the GOT utility under Communication → Transparent Mode and is the recommended setup for online edits when the engineer cannot sit next to the panel.
Cable and Driver Verification
| Cable / Adapter | GOT Connector | Use Case | Notes |
|---|---|---|---|
| GT09-C30USB-5P | GOT RS-422 mini-DIN | PC USB ↔ GOT loader | Mitsubishi proprietary, includes USB-serial electronics |
| GT01-C30R4-25P | FX PLC programming port ↔ GOT RS-422 | GOT ↔ FX3G direct | Only for FX-series PLCs |
| Generic USB-serial + null-modem | GOT RS-232 (D-sub 9-pin) | PC ↔ GOT1000 RS-232 loader | Watch for DB-9 gender and pin 2/3 crossover |
| Standard USB-A → USB-B | GOT front USB slave | Direct GT Designer upload | Recommended — bypasses XPM entirely |
| Pinout (DB-9 PC side) | Signal | DB-9 GOT side | Notes |
| 2 | RXD | 3 (TXD) | Cross |
| 3 | TXD | 2 (RXD) | Cross |
| 5 | GND | 5 | Straight |
| 7, 8 | RTS / CTS | 7, 8 | Loop back if not used |
Verification Checklist
- Device Manager in the XP guest shows the USB-serial adapter and its COM number.
- GT Designer 2
Transfer Setupmatches that COM number, baud, parity, data bits, and stop bits. -
Connection Testreturns success in under 5 seconds. - A
Read from GOToperation transfers the project (typically 0.5–3 MB) without timeout. - The downloaded project opens without "project corrupted" warnings.
- If the project contains scripts or device comments, verify their presence after upload.
Troubleshooting Matrix
| Symptom | Likely Cause | Action |
|---|---|---|
| Connection Test times out, COM number wrong | Guest COM ≠ host COM | Re-check Device Manager inside XPM |
| Adapter not listed in XPM Device Manager | USB arbitration disabled | Enable USB device in XPM toolbar, or pass-through in VMC settings |
| "Communication Error 0xC058" or similar | Baud rate mismatch | Force both sides to 115200 / 8N1 |
| Project reads but is empty / all default | Wrong GOT model selected at transfer | Match the GOT type to the actual hardware (GT1575 ≠ GT1675) |
| Password prompt during upload | GOT project password enabled | Recover password from project source or backup G1/G2 file |
| GT Designer 2 hangs on large project transfer | Insufficient XPM memory | Increase XPM RAM to 1024 MB or more; close other guests |
| Connection works on FX3G but not GOT1000 | GOT loader channel misconfigured | Verify GOT utility communication parameters |
| Cannot find GOT on network | Wrong Ethernet IP / subnet | Use GOT utility IP search; default GOT1000 is 192.168.3.18 |
Migration to GT Designer 3 (Recommended)
GT Designer 2 is no longer the current toolchain. Mitsubishi ships GT Designer 3 (part of GT Works3) as the supported environment for GOT1000 and GOT2000. GT Designer 3 is fully 64-bit and Windows 7/10/11 compatible, removing the need for the XPM guest altogether. The official GT Designer3 Version1 Screen Design Manual (Functions) documents the new transfer-setup menus, the GOT USB driver stack, and the Ethernet / transparent-mode workflows that supersede the XPM-based patterns above.
When migrating:
- Export the GOT1000 project from GT Designer 2 to a G1-format file.
- Open the G1 file in GT Designer 3 and run the project converter.
- Re-select the GOT type — a GT1575-VNBA stays GT15-family; a GT1675-VNBA maps to GT16-family.
- Recompile and upload via the new
Online → Transfer Setupdialog.
Frequently Asked Questions
Why does my USB-serial adapter work for GX Developer to FX3G but not for GT Designer 2 to GOT1000?
The Windows XP Mode guest remaps COM numbers independently from the Windows 7 host. GX Developer was re-pointed to the correct guest COM (e.g. COM5), while GT Designer 2 was still configured for the original desktop COM1. Open Device Manager inside the XP-Mode guest to confirm the live COM number, then update the GT Designer 2 Communication → Transfer Setup to match.
Which COM port should I select for a GOT1000 USB-serial upload in GT Designer 2?
Use the COM number that Device Manager inside the Windows XP Mode guest assigns to the USB-serial adapter (commonly COM3, COM4, or COM5). Pair it with 115200 baud, 8 data bits, no parity, and 1 stop bit, which matches the GOT1000 loader defaults.
Can I use the GOT's front USB port to upload a project from a Windows 7 64-bit host?
Yes. On GT14, GT15, and GT16 hardware the front USB port is a slave port that talks directly to GT Designer. Connect a standard USB-A to USB-B cable, select Transfer Setup → GOT USB in GT Designer 2 or GT Designer 3, and the Windows XP Mode guest is no longer required.
Is FA transparent mode reliable when running GT Designer 2 inside Windows XP Mode?
Only if the PC-to-GOT link is reliable. Transparent mode still uses the same XPM-remapped COM port for the PC side, so the same COM-mapping issue applies. Prefer uploading the GOT project over its front USB port, then run transparent mode against the PLC for online edits.
Can GT Designer 2 upload a project from a GOT1000 through Ethernet?
Yes. Set the GOT's Ethernet parameters in the utility menu (default IP 192.168.3.18, port 5001 for UDP loader), then in GT Designer 2 Transfer Setup choose Ethernet and enter the GOT's IP address. Ethernet is the most robust path on a Windows 7 64-bit host because it avoids the XPM USB-serial stack entirely.