module testbench(); timeunit 10ns; timeprecision 1ns; logic clk_50, clk, rst, cs; logic [1:0] addr; logic [7:0] data_in, data_out; logic rw; logic RXD, TXD; uart dut(.*); always #1 clk_50 = clk_50 === 1'b0; initial begin rst <= '1; repeat(5) @(posedge clk_50); rst <= '0; @(posedge clk_50); end endmodule