Introduction to Sequential Circuits | Digital Electronics
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Introduction to Sequential Circuits
Digital circuits used in our day-to-day life consist of both combinational and sequential circuits. Combinational circuits output only
depends on present inputs. On the other hand, sequential circuits output depends on both present and past inputs, and it has memory
elements.
Combinational Circuits vs. Sequential Circuits
All digital circuits discussed so far are combinational circuits, such as encoder-decoder or adder and subtractor circuits. In
combinational circuits, the output solely depends on the present input and has nothing to do with past inputs.
Sequential circuits output not only depend on present inputs but also on past inputs. Thus, sequential circuits have memory elements. For
example, changing the channel on a television using a remote requires storing the present channel in memory.
Types of Sequential Circuits
There are two types of sequential circuits: synchronous and asynchronous. Synchronous circuits respond to input only at discrete intervals,
while asynchronous circuits immediately respond to input level changes.
Asynchronous Sequential Circuits
In asynchronous sequential circuits, when the input level changes, both the combinational circuit block and memory element immediately
respond to the change. The memory element changes its output state. When the input level changes again, the memory element responds
immediately again.
Synchronous Sequential Circuits
Synchronous sequential circuits respond to input only at discrete intervals of time. These circuits have an additional input, the clock signal,
which changes the state of the memory element only at the discrete interval of time.
ALL ABOUT ELECTRONICS
Introduction to Sequential Circuits
Digital circuits used in our day-to-day life consist of both combinational and sequential circuits. Combinational circuits output only
depends on present inputs. On the other hand, sequential circuits output depends on both present and past inputs, and it has memory
elements.
Combinational Circuits vs. Sequential Circuits
All digital circuits discussed so far are combinational circuits, such as encoder-decoder or adder and subtractor circuits. In
combinational circuits, the output solely depends on the present input and has nothing to do with past inputs.
Sequential circuits output not only depend on present inputs but also on past inputs. Thus, sequential circuits have memory elements. For
example, changing the channel on a television using a remote requires storing the present channel in memory.
Types of Sequential Circuits
There are two types of sequential circuits: synchronous and asynchronous. Synchronous circuits respond to input only at discrete intervals,
while asynchronous circuits immediately respond to input level changes.
Asynchronous Sequential Circuits
In asynchronous sequential circuits, when the input level changes, both the combinational circuit block and memory element immediately
respond to the change. The memory element changes its output state. When the input level changes again, the memory element responds
immediately again.
Synchronous Sequential Circuits
Synchronous sequential circuits respond to input only at discrete intervals of time. These circuits have an additional input, the clock signal,
which changes the state of the memory element only at the discrete interval of time.
