Types of logic circuits
i) Combinational circuits: The logic circuits whose outputs at any instant of time depend only on the input signals present at that time are called combinational circuits.
For a change in input, the output appears immediately, except for the propagation delay through circuit gates.
ii) Sequential circuits: The logic circuits whose output at any instant of time depend not only on the present inputs but also on the past outputs are called sequential circuits.
In sequential circuits, the output signals are fed back to the input side.
Types of Sequential Circuits
i) Synchronous or Clocked circuits: In Synchronous Sequential circuits, synchronization is achieved by a timing device called master-clock generator, which generates a periodic train of clock pulses.
ii) Asynchronous or Unclocked circuits: In an Asynchronous Sequential circuits, events can occur after one event is completed and there is no need to wait for a clock pulse. Therefore, asynchronous circuits are considerably faster than synchronous circuits.
i) Combinational circuits: The logic circuits whose outputs at any instant of time depend only on the input signals present at that time are called combinational circuits.
For a change in input, the output appears immediately, except for the propagation delay through circuit gates.
ii) Sequential circuits: The logic circuits whose output at any instant of time depend not only on the present inputs but also on the past outputs are called sequential circuits.
In sequential circuits, the output signals are fed back to the input side.
It consists of a combinational circuit to which memory elements are connected to form a feedback path.
The memory elements denoted by M are devices capable of storing binary information.
The circuit has m number of external inputs denoted by X and n number of outputs denoted by Z.
The signal value at the output of memory elements denoted by y, are referred to as the present state of sequential circuit.
The external inputs X and present state variables y are applied to combinational circuit, which in turn produces the outputs Z and Y, where Y are referred to as next state of sequential circuit.
To have a sequential circuit, a storage device is required to know what has happened in the past. The basic unit of storage is the Flip-Flop.
Types of Sequential Circuits
i) Synchronous or Clocked circuits: In Synchronous Sequential circuits, synchronization is achieved by a timing device called master-clock generator, which generates a periodic train of clock pulses.
ii) Asynchronous or Unclocked circuits: In an Asynchronous Sequential circuits, events can occur after one event is completed and there is no need to wait for a clock pulse. Therefore, asynchronous circuits are considerably faster than synchronous circuits.
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