Converting period to frequency for a digital clock If a clock waveform has a period of 1.25 µs, what is the corresponding frequency in hertz?

Difficulty: Easy

Correct Answer: 0.8 MHz

Explanation:


Introduction / Context:
Clock specification conversions between period (time per cycle) and frequency (cycles per second) are routine in digital design, timing analysis, and interface selection.


Given Data / Assumptions:

  • Clock period T = 1.25 microseconds.
  • Frequency f = 1 / T.
  • Unit conversions: 1 µs = 10^-6 s.


Concept / Approach:

The inverse relationship f = 1/T directly gives frequency once the period is expressed in seconds. Carefully convert microseconds to seconds to avoid thousand- or million-fold mistakes.


Step-by-Step Solution:

T = 1.25 µs = 1.25 × 10^-6 sf = 1 / T = 1 / (1.25 × 10^-6) HzCompute: 1 / 1.25 = 0.8; and 1 / 10^-6 = 10^6 → f = 0.8 × 10^6 HzTherefore f = 0.8 MHz.


Verification / Alternative check:

Check scale: a period near 1 µs corresponds to near 1 MHz. At 1.25 µs, the frequency should be slightly less than 1 MHz, consistent with 0.8 MHz.


Why Other Options Are Wrong:

  • 8 kHz / 0.8 kHz: off by factors of 10^2–10^3 due to incorrect microsecond conversion.
  • 8 MHz: corresponds to a 0.125 µs period, not 1.25 µs.
  • 12.5 MHz: corresponds to 0.08 µs, far smaller period.


Common Pitfalls:

  • Mixing micro (10^-6) with milli (10^-3).
  • Inverting incorrectly: using f = T instead of f = 1/T.


Final Answer:

0.8 MHz

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