Introduction / Context:
Many counters and frequency dividers rely on a storage element that inverts its state every clock. Recognizing which device exhibits this behavior underlies the design of divide-by-two stages, ripple counters, and synchronous counters.
Given Data / Assumptions:
- The term “toggle mode” refers to an operating condition where Q(next) = Q’(current).
- A J-K flip-flop with J=K=1, or a T flip-flop with T=1, toggles at each active edge.
- Edge-detectors and “toggle detectors” are not storage elements; they do not inherently hold and alternate the state.
Concept / Approach:
A flip-flop is a bistable element. When configured to toggle (J=K=1 for J-K, T=1 for T-type), it changes its state on every active clock edge, producing a square wave at half the input clock frequency. Neither a mere logic “level” nor a detector circuit fulfills the storage and inversion requirements of toggle mode.
Step-by-Step Solution:
Identify devices capable of storing state: flip-flops (D, J-K, T).Recognize toggle configurations: J=K=1 or T=1.Conclude: the device that changes state each qualifying clock pulse is a flip-flop in toggle mode.
Verification / Alternative check:
Example: A J-K flip-flop with J=K=1 divides the input clock frequency by 2 at Q.
Why Other Options Are Wrong:
logic level: Not a device; cannot toggle on its own.edge-detector circuit: Produces narrow pulses, not bistable toggling.toggle detector: Not a standard bistable; typically a sensing circuit.
Common Pitfalls:
Assuming any periodic signal implies a toggling storage element; toggling specifically refers to a bistable’s state inversion.
Final Answer:
flip-flop
Discussion & Comments