Sequential logic is a kind of digital logic whose output depends on both current inputs and the history of earlier inputs. This lesson introduces the idea of circuit state and explains how synchronous circuits use a clock to coordinate state changes.
In combinational logic, the output depends only on the inputs present at that moment. In sequential logic, the output can also depend on the sequence of earlier inputs. Sequential circuits therefore have state, or memory, while combinational circuits do not.
All flashcards
What is sequential logic?
Logic whose output depends on current inputs and stored information from earlier inputs.
What is the state of a sequential circuit?
Stored information representing the circuit’s current condition and helping determine its future behavior.
What does a clock do in synchronous logic?
It coordinates the times when stored values may update; it does not determine the next values.
What is the critical path in a synchronous circuit?
The slowest relevant logic path, which limits the maximum safe clock rate.
What is a race condition in digital logic?
A timing problem in which the outcome depends on which signal arrives first.
Quiz questions
How does asynchronous sequential logic respond to input changes?Answer: It can change state directly without waiting for a clock pulse.
When can a synchronous flip-flop’s output change?Answer: When the flip-flop is triggered by a clock pulse.
What performance benefit can pipelining provide?Answer: Different stages can process portions of work at the same time, improving throughput.
Why can an external input create timing problems in a synchronous circuit?Answer: It may not be synchronized to the circuit’s clock.
Where may asynchronous logic be used in a system that is mostly synchronous?Answer: In selected parts where potential speed benefits are especially valuable.
Based on the Wikipedia article Sequential logic, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.