![]() ![]() The J B and K B inputs are connected to Q A. The J A and K A inputs of FF-A are tied to logic 1. If the "clock" pulses are applied to all the flip-flops in a counter simultaneously, then such a counter is called as synchronous counter. Q BQ A = 00 after the fourth clock pulse. Hence it toggles to change Q B from 1 to 0. This negative change in Q A acts as clock pulse for FF-B. On the arrival of 4th negative clock edge, FF-A toggles again and Q A becomes 1 from 0. So Q B does not change and continues to be equal to 1. Since this is a positive going change, FF-B does not respond to it and remains inactive. On the arrival of 3rd negative clock edge, FF-A toggles again and Q A become 1 from 0. Q BQ A = 10 after the second clock pulse. So it will also toggle, and Q B will be 1. The change in Q A acts as a negative clock edge for FF-B. On the arrival of second negative clock edge, FF-A toggles again and Q A = 0. There is no change in Q B because FF-B is a negative edge triggered FF. ![]() Since Q A has changed from 0 to 1, it is treated as the positive clock edge by FF-B. Initially let both the FFs be in the reset stateĪs soon as the first negative clock edge is applied, FF-A will toggle and Q A will be equal to 1. External clock is applied to the clock input of flip-flop A and Q A output is applied to the clock input of the next flip-flop i.e. But we can use the JK flip-flop also with J and K connected permanently to logic 1. The logic diagram of a 2-bit ripple up counter is shown in figure. It is a group of flip-flops with a clock signal applied. Counter is the widest application of flip-flops. A digital circuit which is used for a counting pulses is known counter. In essence, sequential circuits are much more complicated than combinational ones.Counter is a sequential circuit. In contrast, the output of sequential circuits relies on the current input and also on the previous outputs. The major distinction between these circuits is the outputs of circuits and rely on the current input. Mathematically speaking, outputs solely depend on the inputs. We can define a combinational logic circuit as an electronic circuit whose outputs depend on the condition that its inputs are in. It is the most basic construction block to add two single-bit numbers. Half adder circuits add two binary single-bit numbers, A and B. This assists in linking the feedback data of the past to current information.Ī half adder can be described as a combinatorial logic circuit with two outputs and inputs. A storing element is included to keep the different data about the stable state levels. The sequential circuit contains memory elements. Registers and Flip Flops are a few examples of sequential circuits. However, the possibility of a clock is there in the sequential circuit.ĭemultiplexer, decoder, full adder encoder, and half adder are a few examples of combinatorial circuits. There’s no combinational clock present in a circuit. ![]() On the other hand, the output of the sequential circuit will depend on the recent outputs and current input. The sequential circuit is a digital circuit type whose output relies not just on the current values of the input signals it has but it depends on the past sequence of inputs as well.Īnother distinction between sequential circuits and combinational circuits is that a memory device is absent in combinational circuits.Īn integrated storage unit for sequential circuits can store instant results.Ī circuit’s output from a combined circuit relies on the input at present. A combinational circuit is a digital circuit type where the output is only a pure function of the present input.
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