module adder_A_B_8_bits(
    input [7:0] SW,
    input [0:1] KEY,
    output [0:0] LEDR,
    output [0:6] HEX0, HEX1, HEX2, HEX3, HEX4, HEX5);

    wire [7:0] A, B;
    reg_8_bits_with_areset register(KEY[1],KEY[0],SW,A);
    assign B=SW;

    decoder_hex_16 dozenA(A[7:4],HEX3);
    decoder_hex_16 unityA(A[3:0],HEX2);

    decoder_hex_16 dozenB(B[7:4],HEX1);
    decoder_hex_16 unityB(B[3:0],HEX0);

    reg [7:0] total;
    reg cout;
    assign LEDR[0]=cout;

    decoder_hex_16 dozenTotal(total[7:4],HEX5);
    decoder_hex_16 unityTotal(total[3:0],HEX4);

    always@(*)
        if((A+B)>8'hFF)
            begin
                cout=1;
                total=8'h00;
            end
        else
            begin
                cout=0;
                total=A+B;
            end

endmodule

module reg_8_bits_with_areset(
    input Clk, areset,
    input [7:0] data,
    output reg [7:0] out);

    always@(posedge Clk, posedge areset)
        if(areset)
            out<=0;
        else
            out<=data;
endmodule