In this case, the term synchronous means that the output changes state only at a specified point (leading or trailing edge) on the triggering input called the clock (CLK). What is a flip-flop?įlip-flops are synchronous bi-stable devices, also known as bi-stable multivibrators. These are active-LOW inputs, as indicated by the bubbles on the FF symbol. The commercially used flip-flop has two asynchronous inputs designated as PRESET and CLEAR. Stated in another way, the asynchronous inputs are override inputs, which can be used to override all the other inputs in order to place the FF in one state or the other. These asynchronous inputs can be used to set the FF to the 1 state (known as PRESET) or reset the FF to the 0 state (known as CLEAR) at any time, regardless of the conditions at the other inputs. Most clocked Flip-flops have one or more asynchronous inputs that operate independently of the synchronous inputs (the S, R, J, K, D and T inputs normally referred to as synchronous inputs because their effect on the FF output is synchronized with the clock input). What do you mean by the asynchronous inputs of a flip-flop? When the clock signal changes from high to low state and the output changes due to the inputs, it is called negative edge triggering. If the clock signal changes from low to high state and the output changes due to the inputs, it is called positive edge triggering. The term edge-triggered means that the flip-flop changes its state either at the positive edge (rising or leading edge) or at the negative edge (falling or trailing edge) of the clock pulse and is sensitive to its inputs only at this transition of the clock. Give the difference between positive and negative edge triggering in a flip-flop. To get the desired output from a digital system, flip-flops must be edge-triggered.
When a flip-flop is not edge triggered and the input data changes dynamically, the output will be changed and we cannot obtain the desired output from a digital circuit as per requirement. The term edge triggered means that the flip-flop changes its state either at the positive edge (rising or leading edge) or at the negative edge (falling or trailing edge) of the clock pulse and is sensitive to its inputs only at this transition of the clock. What is edge triggered flip-flop and why is it required? Sequential logic circuits are used as counters, sequence generators and finite state machines. The combinational logic circuits are a part of digital systems and they have many applications such as decoder, encoder, adder, subtractor, multiplexer and de-multiplexer etc.
The basic building block for sequential logic circuits is the flip-flop (FF). Sequential logic circuits are circuits whose outputs at any instant of time depend not only on the present inputs but also on the past outputs. The basic building block for combinational logic circuits is the logic gate. Combinational logic circuits are circuits in which the output at any time depends upon the combination of the input signals present at that instant only, and does not depend upon any past conditions.Combinational logic circuits and sequential logic circuits. What is the difference between combinational and sequential circuits?ĭigital logic circuits are classified into two groups. What is the formula used for total propagation delay calculation in asynchronous binary counters?.What is the difference between latches and flip-flops?.What do you mean by the asynchronous inputs of a flip-flop?.Give the difference between positive and negative edge triggering in a flip-flop.What is edge triggered flip-flop and why is it required?.What is the difference between combinational and sequential circuits?.
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