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?
-
A1 Hz.
-
B60 Hz.
-
C100 Hz.
-
D1000 Hz.
Answer
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.