Digital clock timing: required division of the basic frequency In a standard digital clock application, to generate the “tick” that advances the seconds counter, the basic frequency must be divided down to what rate?

Difficulty: Easy

Correct Answer: 1 Hz.

Explanation:

Introduction / Context:Whether your time base is the mains frequency (50/60 Hz) or a crystal oscillator (for example, 32.768 kHz), a digital clock requires a precise 1 Hz pulse to advance the seconds counter once per second.

Given Data / Assumptions:

  • Seconds increment once each second.
  • Higher-frequency references must be divided (prescaled).
  • Stable division ensures accurate timekeeping.

Concept / Approach:Use a frequency divider so that the output is 1 tick per second. For a 60 Hz input, divide by 60; for 32.768 kHz, divide by 32,768. The exact divider topology may use cascaded binary or BCD counters in HDL.

Step-by-Step Solution:

Identify the reference frequency.Compute division factor to reach 1 Hz.Implement counters in HDL to realize the division.Feed the 1 Hz output to the seconds counter.

Verification / Alternative check:Simulate and measure output period; confirm 1 second between rising edges.

Why Other Options Are Wrong:

  • 60 Hz/100 Hz/1000 Hz correspond to upstream references or debounce rates, not the seconds tick.

Common Pitfalls:Neglecting oscillator tolerance and temperature; consider calibration if needed.

Final Answer:1 Hz.

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