Introduction / Context:
Glitches commonly arise in combinational decoding of multi-bit changing signals, not in the storage elements themselves. This question separates the behavior of counters (sequential storage) from decoders/displays that interpret the count and may require strobing to avoid transient misreads.
Given Data / Assumptions:
- Counters change multiple bits around a clock edge.
- Combinational logic observing those bits can produce hazards during transitions.
- Strobing masks these hazards by enabling observation only during stable intervals.
Concept / Approach:
The counter registers update synchronously at clock edges and, by themselves, do not require “strobing” to function correctly. It is the downstream combinational circuitry (e.g., a binary-to-7-segment decoder) that may need strobing or latching to prevent transient glitches from being displayed or acted upon.
Step-by-Step Solution:
Recognize that flip-flops produce clean logic-level transitions at the clock edge.Identify where glitches originate: unequal path delays in combinational decoders.Apply strobing/latching at the decoder/display interface to mask hazards.Conclude that saying counters “must be strobed” is an overgeneralization and thus incorrect.
Verification / Alternative check:
Observe on an oscilloscope: counter outputs switch cleanly; decoded outputs may momentarily glitch unless gated or latched.
Why Other Options Are Wrong:
Correct: Misattributes the need for strobing to the counter block rather than the decoder.Only for Gray-coded / Johnson counters: Glitch behavior is about decoding transitions, not about a particular counter code alone.
Common Pitfalls:
Assuming any multi-bit change implies the source (counter) is glitchy.Neglecting to synchronize the strobe window with stable data timing.
Final Answer:
Incorrect
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