carry_select_4bit.v.bak

module carry_select_4bit(A, B, cin, S, cout);
	input [3:0] A, B;
	input cin;
	output [3:0] S;
	output cout;

	wire [3:0] W0, W1;
	wire [1:0] Wcout; //carry out bits for ripple carries for cin of 0 and 1

	assign carry[0] = cin;

	//ripple carry outputs for cin of 0 and 1
	ripple_4bit rip0 (.A(A), .B(B), .cin(0'b0), .S(W0), .cout(Wcout[0]));
	ripple_4bit rip1 (.A(A), .B(B), .cin(0'b1), .S(W1), .cout(Wcout[1]));
	
	//construct multiplexor gates to decide which ripple carry solution to use,
	//select signal is cin (carry in)
	genvar i;
	generate begin:mux_loop
		for (i = 0; i < 3; i = i +1) begin
			multiplexor M0 (.w0(W0[i]), .w1(W1[i]), .s(cin));
		end
	endgenerate

	//generate carrout bit
	multiplexor M5 (.w0(Wcout[0]), .w1(Wcout[1]), .s(cin));

endmodule