# Lab 8
Name: Manan Chavda
Roll No.: CS22B017

---
## Question 1

module full_add_testbench;
reg a,b,cin;
wire sum,cout;
Fulladder f1(.a(a),.b(b),.c(cin),.sum(sum),.carry(cout));
initial
begin
a=1'b0;b=1'b0;cin=1'b0;
#100 a=1'b0;b=1'b0;cin=1'b1;
#100 a=1'b0;b=1'b1;cin=1'b0;
#100 a=1'b0;b=1'b1;cin=1'b1;
#100 a=1'b1;b=1'b0;cin=1'b0;
#100 a=1'b1;b=1'b0;cin=1'b1;
#100 a=1'b1;b=1'b1;cin=1'b0;
#100 a=1'b1;b=1'b1;cin=1'b1;
end
endmodule

module Fulladder(a,b,c,sum,carry);
input a,b,c;
output sum,carry;
wire x,y,z;
Halfadder h1(.a(a),.b(b),.sum(x),.carry(y));
Halfadder h2(.a(x),.b(c),.sum(sum),.carry(z));
or o1(carry,y,z);
endmodule

module Halfadder(a,b,sum,carry);
input a,b;
output carry,sum;
assign sum = a^b;
assign carry = a*b;
endmodule

___
## Question 2

module RippleCarryAdder(
input [3:0]a,b,
input c,
output carry,
output [3:0]sum);
wire c1,c2,c3
Fulladder f1(.a(a[0]),.b(b[0]),.c(c),.sum[0],.carry(c1));
Fulladder f2(.a(a[1]),.b(b[1]),.c(c1),.sum[1],.carry(c2));
Fulladder f3(.a(a[2]),.b(b[2]),.c(c2),.sum[2],.carry(c3));
Fulladder f4(.a(a[3]),.b(b[3]),.c(c3),.sum[3],.carry(carry));
endmodule
//As fulladder is used in ripple carry adder we use it here.
module Fulladder(a,b,c,sum,carry);
input a,b,c;
output sum,carry;
wire x,y,z;
Halfadder h1(.a(a),.b(b),.sum(x),.carry(y));
Halfadder h2(.a(x),.b(c),.sum(sum),.carry(z));
or o1(carry,y,z);
endmodule

module Halfadder(a,b,sum,carry);
input a,b;
output carry,sum;
assign sum = a^b;
assign carry = a*b;
endmodule

//Testbench:
module rca_testbench;
reg[3:0] a,b;
reg c;
wire[3:0] sum;
wire c4;
rca uut(a,b,c,c4,sum);
initial
begin
c=0;
a = 4’b0001;b= 4’b1000;//Here I have taken two cases for a and b not all the cases as said in the question.
#100
a = 4’b1111 ; b = 4’b1001;
end
endmodule

___
## Question 3

module Multiplexer(input a, b, s, output u);
    assign u = (s == 1'b0) ? a : b;
endmodule
//testbench
module MX_testbench;
    reg a, b, s;
    wire u;
    Multiplexer m1(.a(a), .b(b), .s(s), .u(u));
    initial
    begin
        #100 a = 1'b0; b = 1'b0; s = 1'b0;
        #100 a = 1'b0; b = 1'b0; s = 1'b1;
        #100 a = 1'b0; b = 1'b1; s = 1'b0;
        #100 a = 1'b0; b = 1'b1; s = 1'b1;
        #100 a = 1'b1; b = 1'b0; s = 1'b0;
        #100 a = 1'b1; b = 1'b0; s = 1'b1;
        #100 a = 1'b1; b = 1'b1; s = 1'b0;
        #100 a = 1'b1; b = 1'b1; s = 1'b1;
    end
endmodule

___