`timescale 1ns/1ns
module data_select(
input clk,
input rst_n,
input signed[7:0]a,
input signed[7:0]b,
input [1:0]select,
output reg signed [8:0]c
);
always@(posedge clk or negedge rst_n) begin
if(~rst_n) begin
c <= 9'd0;
end
else begin
case(select)
0: c <= a;
1: c <= b;
2: c <= a + b;
3: c <= a - b;
default: c <= 9'd0;
endcase
end
end
endmodule