Clock Frequency Calculator Formula
Understand the math behind the clock frequency calculator. Each variable explained with a worked example.
Formulas Used
Clock Period
period_ns = 1e9 / clock_hzInstructions per Second
mips = clock_hz / cycles_per_instruction / 1e6Timer Tick Frequency
timer_freq = clock_hz / prescalerTimer Tick Period
timer_period_us = prescaler / clock_hz * 1e6Variables
| Variable | Description | Default |
|---|---|---|
clock_freq_mhz | Clock Frequency(MHz) | 16 |
cycles_per_instruction | Cycles per Instruction | 1 |
prescaler | Timer Prescaler | 64 |
clock_hz | Derived value= clock_freq_mhz * 1e6 | calculated |
How It Works
Clock Frequency and Timer Calculations
The clock frequency determines the speed of all operations in a microcontroller.
Formulas
Clock Period = 1 / Frequency
MIPS = Clock Frequency / Cycles per Instruction
Timer Frequency = Clock / Prescaler
Prescalers divide the clock to create slower timer ticks, useful for generating precise time intervals without consuming CPU cycles.
Worked Example
16 MHz clock, 1 CPI (ARM Cortex-M), prescaler of 64.
- 01Clock period: 1 / 16e6 = 62.5 ns
- 02MIPS: 16e6 / 1 = 16 MIPS
- 03Timer frequency: 16e6 / 64 = 250,000 Hz
- 04Timer tick: 64 / 16e6 = 4.000 microseconds
Frequently Asked Questions
Does higher clock speed always mean faster execution?
Not necessarily. Pipeline stalls, memory wait states, and bus bottlenecks can reduce effective throughput.
What prescaler should I use?
Choose the prescaler that gives timer resolution suitable for your application while fitting the desired period within the counter range.
Why does my microcontroller run slower than the crystal?
Check for prescaler settings, PLL configuration, and wait states. Some MCUs divide the oscillator internally by default.
Ready to run the numbers?
Open Clock Frequency Calculator