Write a 4 bit ripple adder that uses instances of this fulladder FA shown below,

Question

Write a 4 bit ripple adder that uses instances of this fulladder FA shown below, A and B are inputs, Cin is the carry in, Sum is the output sum, Cout is the carry out, and OF indicates overflow which is determined by the (carryin to the last bit) xor (the carry out) module FA( input A, B, Cin, output C, Cout ); assign C = (Ang) assign Cout A&B; | A&Cin; | B&Cin; endmodule ACin; // this is you 4 bit ripple adder, fill in your code using instances of FA module FA4(input [3:0] A, B, input Cin, output [3:0] Sum, output Cout, OF );

Explanation / Answer

Code : Full Adder

module FA(   

input A,B,Cin

output C,Cout

);

assign C = (A^B)^Cin;

assign Cout = A&B | A&Cin | B&Cin;

endmodule

Code : 4 Bit Ripple Carry Adder

module FA4(   

input [3:0] A,B,

input Cin

output [3:0] Sum,

output Cout, OF

);

wire c1,c2;

FA FA_1(A[0],B[0],Cin,Sum[0],c1),

FA_2(A[1],B[1],c1,Sum[1],c2),

FA_3(A[2],B[2],c2,Sum[2],OF),

FA_4(A[3],B[3],OF,Sum[3],Cout);

endmodule

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