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DIGITAL LOGIC CIRCUITS PDF

Tuesday, March 26, 2019


LOGIC OPERATIONS AND TRUTH TABLES. Digital logic circuits handle data encoded in binary form, i.e. signals that have only two values, 0 and 1. Binary logic. Digital describes any system based on discontinuous data or events. Logic gate circuits are designed to input and output only two types of signals: “high”. Digital Logic Circuits form the basis of any digital (computer) system. features of digital logic circuits, which are at the heart of digital computers. Digital Logic.


Digital Logic Circuits Pdf

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electronic circuits that convey information, including logic gates. Digital Digital Logic Design is used to develop hardware, such as circuit boards and microchip . This material has been developed for the first course in Digital Logic Design. The content is Digital Design Overview (from Transistor to Super Computer). Combinational logic circuits. – Sequential logic circuits. – How digital logic gates are built using transistors. – Design and build of digital logic systems.

The small circle represents inversion. The outputs of all NOR gates are low if any of the inputs are high. The symbol is an OR gate with a small circle on the output. An encircled plus sign is used to show the EOR operation.

It will give a low output if either, but not both, of its two inputs are high. The symbol is an EXOR gate with a small circle on the output.

XOR has a significant role among the logic gates because of its functionality. The realization of multiplexer is clearly explained in [15]. The advantage of proposed design is simple in structure compared to the 3-input majority gate existing designs.

It requires one 3-input majority gate and one 5- input majority gate, and it requires only 28 cells for its construction. The proposed XNOR is the first design implemented with 5-input majority gate based multiplexer. The conventional design of XNOR structure constructed with basic gates requires three gates and two inverters.

Whereas, the proposed XNOR gate requires one 3-input majority gate, one 5-input majority gate, and two inverters. As a first time, the proposed sequential logic elements are tried to realize with 5-input Majority gate based multiplexer. The below Fig.

All the D-latch is a device it just transfers data from input to output when the enable is activated. D flip-flop is formed by using the D-latch. The D Flip-flop is widely used in various registers and counters.

D-Flip-flop also used as a memory element in a serial adder to store the carry as well as in serial comparator [21, 22]. It is also known as a "data" or "delay" flip-flop.

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The proposed D-latch requires 39 cells instead of 42 cells used in existing D-latch, and also it requires fewer clocks compared to existing one. The cost of circuits depends on Area and Delay [23].

Hence, the cost of proposed design is less with reduced cells and delay compared to previous designs. The D-latch is shown in Fig.

The D flip-flop captures the value of the D-input at a particular portion of the clock cycle such as the rising edge of the clock and the same appears as the Q output. The D flip-flop can be viewed as a memory cell, a zero-order hold, or a delay line.

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The D flip-flop requires 25 cells instead of 30 cells used in existing design, and also it requires two clock zones instead of 4 clock zones used in existing D flip-flop. Equation 4 is used to implement the D flip-flop as shown in Fig. A latch has exactly two stable states.

A T-latch is very similar to T Flip-flop, but it is not synchronous with the clock. T-latch has a feedback path so that the stored information toggles.

T-latch schematic and layout using 5 is as shown in Fig. The T flip-flop is also known as Toggle flip-flop. T flip-flop is extensively used in synchronous and asynchronous counters.

Whenever, the clock input is high, the T flip-flop changes state "toggles". If the clock input is low, the flip-flop holds the earlier value. This functionality is described by the characteristic equation 6.

The T flip-flop realization regarding majority gates using 7 and its layout is shown in Fig. As seen from the schematic and layout diagrams, the proposed sequential logic elements require only two gates i. The following Table I gives the performance review of proposed designs compared with existing designs.

Table I gives the clear idea about the number of majority gates, cell count, and clock zones required by the proposed designs regarding recent existing designs.

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Due to the limitation of space, the area is not included. But, as the number of cells decreases automatically the area occupied by the QCA circuit also reduces. Even though recently the D flip-flop is proposed in [27], but this design requires 33 cells and five clock zones.

Therefore, after analyzing the various existing designs, the digital logic circuits proposed in [13] are efficient and different existing designs are also compared in [13]. Hence, here the proposed designs comparison provided with [13] only.

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The proposed design uses five input majority gate based multiplexer [15]. The main advantage of five input majority gate is we can configure the input according to our requirement, particularly in complex logic function applications and this advantage is most useful to reduce the number gates. As seen from the table the XOR gate have The similar improvements can be achieved in XNOR gate.

Both logic gates have a delay of 3 clock zones similar to previous designs with reduced gates and cells. Similarly, in D-latch gate count is reduced by The T-latch has The simulation results of XOR gate is shown in Fig.

In QCA circuit, one complete clock cycle contains four clock zones titled as clock 0, clock 1, clock 2, and clock 3. As seen from the Fig. Truth tables are used to help show the function of a logic gate.

If you are unsure about truth tables and need guidence on how go about drawning them for individual gates or logic circuits then use the truth table section link. Digital systems are said to be constructed by using logic gates.

The basic operations are described below with the aid of truth tables. It will give a low output if either, but not both , of its two inputs are high. The symbol is an EXOR gate with a small circle on the output.Also note that a truth table with 'n' inputs has 2 n rows. Similarly, in D-latch gate count is reduced by Fast Adder Designs, Tradeoffs, and Examples.

Springer International Publishing, A T-latch is very similar to T Flip-flop, but it is not synchronous with the clock. The aim of this experiment was achieved.

In hold phase, the inter-dot barrier is very high, and cells retain polarity and acts as inputs to neighbor cells. Pp