Sequential Logic: Flip-Flops, Counters, and Memory
Circuits That Remember
State and timing
Sequential logic depends on previous inputs as well as current ones. Flip-flops store one bit of state, and clocks coordinate when that state updates. Registers, counters, and finite-state machines are all built from these memory elements.
Sequential logic terms
Timing matters
Sequential circuits can fail if signals change too close to a clock edge. Setup and hold times are essential to reliable operation.
What is the primary function of a flip-flop?
A flip-flop is a one-bit memory element.
Correct answer: Store one bit of state
What signal usually controls when a flip-flop updates?
Most flip-flops change state on a clock edge.
Correct answer: clock
A counter is most directly used to
Counters step through states to count pulses or events.
Correct answer: Count events or cycles
Why are setup and hold times important?
Inputs must be stable around the clock edge so the flip-flop can store the intended value.
Correct answer: to ensure reliable capture
Building a simple state circuit
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Step 1: Identify what information must be remembered.
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Step 2: Choose an appropriate storage element such as a flip-flop.
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Step 3: Define the clocking and reset behavior.
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Step 4: Verify timing constraints and state transitions.