Digital clock HDL design clarification: Is frequency prescaling used to convert a 1 pulse-per-second (1 pps) input into a 60 pulses-per-second (60 pps) timing signal for the clock?

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Solve this multiple-choice question and choose the correct option.

Accepted Answer

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

Digital clock HDL design clarification: Is frequency prescaling used to convert a 1 pulse-per-second (1 pps) input into a 60 pulses-per-second (60 pps) timing signal for the clock?

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