Therefore these are some difference between sequential and combinational circuit. On other hand Sequential circuit is mainly used for storing data. On other hand building blocks for sequential circuit are flip flops.Ĭombinational circuit are mainly used for arithmetic as well as Boolean operations. However on other hand implementation of feedback makes sequential circuit more complex as compared to combinational circuit.Įlementary building blocks for combinational circuit are logic gates. No implementation of feedback makes the combinational circuit less complex as compared to sequential circuit. On other hand Sequential circuit are comparatively slower and has low performance as compared to that of Combinational circuit. On other hand in case of Sequential circuit output relies on its previous feedback so output of previous input is being transferred as feedback used with input for next output generation.Īs the input of current instant is only required in case of Combinational circuit, it is faster and better in performance as compared to that of Sequential circuit. In Combinational circuit as output does not depend on the time instant, no feedback is required for its next output generation. Now let’s illustrate the difference between that of Synchronous and Asynchronous Sequential Circuits with the example of a Synchronous and Asynchronous 2-bit binary UP Counter using T-Flip-Flops. On other hand Sequential circuit is the type of circuit where output not only relies on the current input but also depends on the previous output. This means that a Sequential Circuit having ‘N’ Flip-Flops can be in at most Internal States. N.Ĭombinational Circuit is the type of circuit in which output is independent of time and only relies on the input present at that particular instant. The block diagram of combinational circuit is given below:ĭifference between these two circuits is given below: S. This is in contrast to sequential logic in which the output depends upon not only on the present input but also on the history of input. In digital circuit theory, a combinational logic is a type of digital logic which is implemented by Boolean circuit, where the output is a pure function of the present input only. Design Procedure of Sequential Logic Circuits. the sequential circuits use current input variables and previous input variables which are stored and provide the data to the circuit on the next clock cycle. The Block diagram for sequential circuit is given below: A sequential circuit is a combination of a combinational circuit and a storage element. Although every digital system is likely to have a combinational circuits, most systems encountered in practice also include memory elements, which requires that the system be describes in term of sequential circuit. With the applied inputs to the combinational logic, the circuit outputs are derived. But the logical structure is very similar.A sequential circuit is the assimilation of a combinational logic circuit and a storage element.fewer transistors, much more dense, relies on electrical properties.This is a not the way actual memory is implemented.Address Space: number of locations(usually a power of 2) k = 2n locations Addressability: number of bits per location(e.g., byte-addressable) m bitsĢ2 x 3 Memory word WE word select input bits address write enable address decoder output bits Now that we know how to store bits,we can build a memory – a logical k × m array of stored bits.When WE=1, n-bit value D is written to register.We use a collection of D-latches, all controlled by a common WE.when WE = 0, latch holds previous value.when WE = 1, latch is set to value of D.Two inputs: D (data) and WE (write enable).final state determined by electrical properties of gates. 1 0 0 1 0 1 1 Then set S=1 to “store” value in quiescent state.
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