`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)
		c <= 0;
	else begin
		case(select)
			2'd0: c <= a;
			2'd1: c <= b;
			2'd2: c <= a + b;
			2'd3: c <= a - b;
			default: c <= 0;
		endcase
	end
end
endmodule