Difficulty: Easy
Correct Answer: 1 pulse every 10 minutes
Explanation:
Introduction / Context:Digital clocks represent minutes with two cascaded counters: a MOD-10 for units (0–9) and a MOD-6 for tens (0–5). Understanding the carry/rollover behavior between these counters is essential to design correct timing chains in HDL.
Given Data / Assumptions:
Concept / Approach:The tens-of-minutes counter must increment once for every ten minutes elapsed, because the units-of-minutes runs from 0 to 9 each minute. Thus, its input rate is one-tenth the minutes-units input rate.
Step-by-Step Solution:
Minutes-units (MOD-10) input: 1 pulse per minute.Units roll over every 10 minutes → emit a carry pulse.Tens-of-minutes (MOD-6) increments on that carry.Therefore, tens-of-minutes input = 1 pulse every 10 minutes (i.e., 6 per hour).Verification / Alternative check:Timing diagram over one hour shows six increments of the tens-of-minutes counter at 00, 10, 20, 30, 40, and 50 minutes.
Why Other Options Are Wrong:
Common Pitfalls:Feeding the tens counter directly with the 1-minute tick rather than the units’ carry line leads to an illegal 0–5 sequence every minute.
Final Answer:1 pulse every 10 minutes
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