## Q8: MOD 8 Counter

Q-Implement a MOD-8 counter using Parallel-in Parallel-out register and Adder. Ans: We have a 3-bit register with two common inputs CLK & CLEAR for all 3 FFs. So we initiate the counter we clear all the FFs and then give clock.  Whenever count reaches 7 output of adder becomes 000 with carry 1 and carry is […]

## Q10: Implement ALU using MUX & ADDER

Q- Implement a basic ALU which performs the operations of logical AND, logical OR, ADD, SUBRACT depending on the values of S1 & S0 Ans: We need to use an ADDER, AND gate, OR gate and some MUXes to implement the above function. We select the functions using the two variables S0 & S1 as: S1           […]

## Q8: Implement function using MUX & ADDER

Q- Design and implement the following logical functions with a combinational circuit (with A and B being 4-bit numbers): S1           S0           Output 0              0              A OR B 0              1              A AND B 1              0              A’ 1              1              A XOR B Ans:  The following circuit would give the required outputs:

## Q7: Implement function using MUX & ADDER

Q- Design and implement the following with a combinational circuit (with A and B being 4-bit numbers): S2           S1           S0                           Output 0              0              0                              2A 0              0              1                              A plus B 0              1              0                              A plus B’ 0              1              1                              A minus 1 1              0              0                              2A + 1 1              0              1                              A plus B […]

## Q6: Implement function using MUX & ADDER

Q- Design and implement the following with a combinational circuit (with A and B being 4-bit numbers): S1           S0                           Output 0              0                              A plus B 0              1                              left shift A 1              0                              A plus B plus 1 1              1                              2A + 1 Ans: We need one 4-bit parallel ADDER and MUX to implement the above. As […]

## Q3: Implement equations using Half Adders

Q- Implement the following equations using only Half Adder circuits. D= A XOR B XOR C E = A’BC + AB’C F = ABC’ + (A’+B’) C G= ABC Ans: We know the equations for Half Adder are S = A xor B           and        C = AB And can be represented as follow: We have […]

## Question: 4-bit ADDER and SUBTRACTOR in a SINGLE CIRCUIT

Q- Implement the 4-bit ADDER and SUBTRACTOR in a single circuit where we select one of the two using a select pin SEL. Ans: The following circuit would work as required: In this circuit we use property of XOR gate by which XOR gate acts as a inverter when we have one input as 1. When sel = […]

## Question: Implement Subtractor using Adder

We can also do subtraction using adders. As we have already studied that we can do subtraction by 2’s compliment method in which we add 2’s compliment of subtrahend to minuend and 2’s compliment can be found by inverting all bits of subtrahend and then adding one. So we have to do as F= A […]

## Q-Implement BCD to Excess 3 converter using parallel adder

Ans: As we know to get Excess-3 from BCD we need to add 3 (0011) to the BCD number. So the circuit to implement the above is: