Difficulty: Easy
Correct Answer: a Johnson shift counter
Explanation:
Introduction / Context:Digital systems often require multiple repetitive timing waveforms with specific phase relationships. Counters and shift registers can generate such patterns for scanning displays, timing state machines, and frequency division. One classic solution is the Johnson (twisted-ring) counter.
Given Data / Assumptions:
Concept / Approach:A Johnson shift counter is a feedback shift register where the complement of the last stage is fed to the first. With n flip-flops it produces 2n unique states, each corresponding to a distinct output pattern across the register taps. These taps provide multiple repetitive waveforms with defined duty cycles and phase offsets.
Step-by-Step Solution:
Consider a 4-stage Johnson counter → 8 unique states.Each stage output toggles in a regular pattern, generating multiple square-like waveforms.The outputs are evenly distributed in phase, ideal for sequencing LEDs or multiplexers.Therefore, among the given options, a Johnson shift counter best fits the description.Verification / Alternative check:Compare with a simple ring counter (no inversion feedback). Johnson counters double the state count for the same number of stages and provide rich waveform sets, often preferred for pattern generation.
Why Other Options Are Wrong:
Common Pitfalls:Confusing a clock oscillator (which outputs a single square wave) with a counter-based sequencer that provides several distinct outputs. Johnson counters require a clock source but provide multiple phased outputs.
Final Answer:a Johnson shift counter
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