TM172PDG42RI: WDT:0 Error & Infinite Reboot Loop during USB Program Download

[StevenCho]

Hello,

I am writing to share a recurring technical issue I have encountered with the TM172 series controllers (including models TM172PDG18R and TM172PDG42RI) regarding USB program downloads.

Issue Description:

When attempting a program download via USB to a new, unconfigured TM172 controller, the device triggers a "WDT:0" (Watchdog Timer) error, resulting in an infinite reboot loop.

Observations & Testing:

• Symptom: The device fails to boot correctly after the USB download, effectively locking it in a reboot cycle.
• Workaround: I have confirmed that performing a BIOS download (firmware update) on the unit resolves the issue, allowing the program to run normally.
• Testing: We have tested this across multiple hardware versions and firmware/software configurations. While matching the PLC firmware with the specific HVAC software target version mitigates the problem, this manual update process is difficult to manage in field environments.

The Challenge:

Many of our end-users rely on standardized USB program downloads for field maintenance, similar to their experience with other products like Vijeo Designer Basic, where the firmware update process is handled seamlessly during the download. Requiring field technicians to manually update the BIOS before a standard program download creates significant usability friction and customer dissatisfaction.

Question/Feedback:

1. Is there a fundamental improvement or roadmap to integrate firmware handling into the USB download process for future versions of the TM172 series?
2. Are there any other way to upgrade bios by using USB?
   Like a Machine Expert Product(M241/251/262)

Thank you in advance.

Regards, Steven Cho

[FedericoM]

Hello,

what you are experiencing shouldn't happen, could you please send me an email with details about the units which have this unexpected watchdog.

It would be good if you can send me a picture of the PLC label on the back so we can trace the production week and other information.

Please write this info to federico.marcassa@se.com.

About your questions:

- BIOS can be update using USB pendrive, you can't update bios and application, but as I wrote above, it is not necessary, you are experiencing an unexpected behavior.

- BIOS and application can be updated in one shot on TM173O, because in this case it is required an alignment between bios version and compiled application

Thank you

[StevenCho]

Thank you, Federico🙂

I just sent a mail that contain the detail information.

Thank you.

Regards, Steven Cho