A current-time comparison can appear to work in the simulator yet stop working after download to a Nannoline controller without a real-time clock (RTC). The simulator can use the computer's current time; the controller has no independent real-time source.
Why the Comparison Stops After Download
Keeping the programming connection attached does not make the computer's clock the controller's clock. The evidence confirms only simulator-side access to PC time, not transfer or synchronization of that time to the controller.
Simulator and Controller Behavior
| Execution environment | Time source | Current-time comparison |
|---|---|---|
| Simulator | Computer time | Can produce a meaningful result |
| Controller without RTC | No confirmed real-time source | Cannot make a meaningful current-time comparison |
Time Data Without an RTC
The controller may still permit access to memory associated with time data, but those contents have no established real-time meaning without an RTC. Do not treat readable values as proof that the controller knows the current date or time.
The evidence does not identify every unavailable function. Use a functional rule: any operation that depends on the actual current time cannot be relied upon unless another documented mechanism supplies and maintains that time.
Verification Procedure
- Run the logic in the simulator and confirm that the comparison follows the computer's current time.
- Download the same logic to the controller without an RTC.
- Monitor the time data and comparison result. If they no longer track the computer clock, confirm that the programming connection is not acting as a time source.
- Do not release the application until a documented controller time source is available or the logic is redesigned so it does not require current time.
FAQ
Can Nannoline current-time compare work without an RTC?
Not as a meaningful real-time comparison. Without an RTC or another documented time source, the controller does not have confirmed current time to compare.
Why does current-time compare work in the simulator but not the controller?
The simulator can compare against the computer's clock. After download, the controller executes independently and the attached communication port does not provide a confirmed time feed.
Can I use the computer clock while the controller stays connected?
The evidence does not establish any automatic clock transfer through the programming connection. Use the PC clock only if the product documentation provides an explicit synchronization mechanism; otherwise redesign the logic or use RTC-equipped hardware.
