Description
For down counting use reload minus subsecondRegister; for up counting use the register itself.
Timer formulas depend on whether endpoints are inclusive, the count direction, prescaling, and wrap behavior. A counter reading alone cannot reveal an arbitrary number of elapsed wraps.
For down counting use reload minus subsecondRegister; for up counting use the register itself.
When to use this tool
Use Microcontroller: RTC Sub Second Register Fraction when you need a timer period, wrap delta, or explicit count-budget term.
How to use the tool and how it works
- Enter subsecondRegister, reload, countDirection. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read result. Expand result to inspect the returned fields.
For down counting use reload minus subsecondRegister; for up counting use the register itself. Divide by reload + 1 for elapsedFraction.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| subsecondRegister | Subsecond Register | Required. Safe integer. |
| reload | Reload | Required. Safe integer. |
| countDirection | Count Direction | Required. Text; one of "up", "down". Implementation limit: 8192 Unicode code points and 16384 UTF-16 code units. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Result | Required. Object. |
| result.elapsedFraction | Elapsed Fraction | Calculated result member: number. |
{
"input": {
"subsecondRegister": 7,
"reload": 9,
"countDirection": "down"
},
"output": {
"result": {
"elapsedFraction": 0.2
}
}
}Limitations and assumptions
- The supplied register must be within the inclusive reload range; synchronization and device-specific RTC behavior are not handled.
- Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Check the timer mode and register semantics in the device documentation, including synchronization and latency.
References
Similar or alternative tools
- RTC Subsecond Downcounter Elapsed
Subtract counter from reload for elapsedTicks and divide by reload + 1 for fraction.
- Timer Prescale Resolution
Divide positive prescaler by clockHertz for tickSeconds and multiply by nonnegative tickCount for durationSeconds.