Introduction / Context:
Digital clocks in hardware description languages (HDLs) often use frequency division to derive human-time signals from a faster reference. This question tests your understanding of “frequency prescaling” and whether it is used to convert a slow 1 pps source into a faster 60 pps signal.
Given Data / Assumptions:
- A 1 pps signal provides one pulse each second.
- A 60 pps signal provides sixty pulses each second.
- “Frequency prescaling” and “frequency division” traditionally reduce frequency (divide), not multiply.
- Clock projects typically derive 1 pps by dividing a higher-frequency reference (for example, 60 Hz or a crystal oscillator).
Concept / Approach:
A prescaler divides the input frequency: fout = fin / N. To go from 60 pps to 1 pps, choose N = 60. To go from 1 pps to 60 pps would require frequency multiplication or a different, faster source; division cannot increase frequency.
Step-by-Step Solution:
Identify the goal: obtain 60 pps from 1 pps.Recall prescaler behavior: fout = fin / N, where N ≥ 1.If fin = 1 pps, division can create 1/N pps ≤ 1 pps, never 60 pps.Therefore, the statement that prescaling turns 1 pps into 60 pps is not valid.
Verification / Alternative check:
Common digital clock designs divide 60 Hz mains or a high-frequency crystal down to 1 Hz (1 pps), not the other way around.
Why Other Options Are Wrong:
Correct: Would imply prescaling increases frequency; it does not.Applies only for mains-driven clocks: Source type does not change the divide-only nature of prescaling.Valid only for BCD clocks: Code format (BCD) is unrelated to frequency multiplication.
Common Pitfalls:
Confusing dividers (prescalers) with phase-locked loops or numerically controlled oscillators that can multiply.Assuming any “timing block” can arbitrarily change frequency up or down.
Final Answer:
Incorrect
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