`timescale 1ns/1ns module data_minus( input clk, input rst_n, input [7:0]a, input [7:0]b, output reg [8:0]c ); always @(posedge clk or negedge rst_n) begin if (!rst_n) begin c<=0; end else begin c<=(a>b?(a-b):(b-a)); end end endmodule