[HDLBits] Exams/ece241 2014 q1c

Assume that you have two 8-bit 2's complement numbers, a[7:0] and b[7:0]. These numbers are added to produce s[7:0]. Also compute whether a (signed) overflow has occurred.

module top_module (
    input [7:0] a,
    input [7:0] b,
    output [7:0] s,
    output overflow
); //
    assign s=a+b;
    assign overflow=(a[7]==b[7]) ? s[7]^a[7] : 0;
    // assign s = ...
    // assign overflow = ...

endmodule

直接加，倘若产生进位则会因为位数不够，被舍弃。overflow位根据补码加法规则生成