The circuit diagram and truth table is shown below.Ī clock pulse is given to the inputs of the AND Gate. This problem can be overcome by using a bistable SR flip-flop that can change outputs when certain invalid states are met, regardless of the condition of either the Set or the Reset inputs.įor this, a clocked S-R flip flop is designed by adding two AND gates to a basic NOR Gate flip flop.
The problems with S-R flip flops using NOR and NAND gate is the invalid state. If both the values of S and R are switched to 1, then the circuit remembers the value of S and R in their previous state. They are supposed to be compliments of each other. If both the values of S and R are switched to 0 it is an invalid state because the values of both Q and Q’ are 1. In both the states you can see that the outputs are just compliments of each other and that the value of Q follows the compliment value of S. Like the NOR Gate S-R flip flop, this one also has four states. The circuit of the S-R flip flop using NAND Gate and its truth table is shown below.įig.2 SR Flip-flop Using Nand gates Operation This is an invalid state because the values of both Q and Q’ are 0. If both the values of S and R are switched to 0, then the circuit remembers the value of S and R in their previous state. In both the states you can see that the outputs are just compliments of each other and that the value of Q follows the value of S.
By 3 Flip flop we get output as 2 3-1= 7 to 0.Fig.1 SR Flip-flop Using NOR gates Operationįrom the diagram it is evident that the flip flop has mainly four states. We get output(state changes) after every -ve edge clock pulse. Therefore, we get output(as down counting Q3(MSB) Q2 Q1(LSB) after 8th -ve edge triggered clock the output of the three Flip flops again becomes Q3 = 0, Q2 = 0, Q1 =0. Therefore, Flip flop 3 output is toggle when there is clock falling edge and Q’2=1 and Q’1 = 1. Similarly, Flip flop 3 toggle input(T) is connected to Q’2 and Q’1. Therefore, Flip Flop 2 output state Q 2 is toggle only when there is clock falling edge (i.e -ve edge triggering) and Q’ 1 =1. Flip-flop(FF) 2 toggle input(T2) is connected to Q’ 1. In simplified equation of K map we get T 1 = 1, therefore Flip flop 1 output Q 1 is toggle for every negative edge(because clock is negative edge triggered). Here -ve edge triggered clock is used for toggling purpose.Īs we see from characteristics table when T = 1, then toggling takes place and T =0 then it stores the output state. Timing diagram of 3 bit synchronous Down counter. Program for Binary To Decimal Conversion. Program for Decimal to Binary Conversion. TIMING DIAGRAM EDGE TRIGGERED FLIP FLOP CODE
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