//-----------------------------------------------------------------------------//  //  Copyright (c) 2009 Xilinx Inc.////  Project  : Programmable Wave Generator//  Module   : lb_ctl.v//  Parent   : wave_gen//  Children : debouncer.v////  Description: //     Loopback controller.//     Implements a debouncer on a slide switch, which is used to select//     the output on the txd pin. When "off" (connected to gnd, so low), the //     normal transmit path is selected. When "on" (high), the rxd pin is//     looped back to the txd pin with no intervening logic (a pure//     combinational path)////  Parameters://     CLOCK_RATE:     Clock rate (in Hz)//     DEBOUNCE_TIME:  In SECONDS (real)////  Local Parameters:////  Notes       : ////  Multicycle and False Paths//     None`timescale 1ns/1psmodule lb_ctl (  input            clk_tx,          // Clock input  input            rst_clk_tx,      // Active HIGH reset - synchronous to clk_tx    input            lb_sel_i,        // Undebounced slide switch input    input            txd_tx,          // Normal transmit data  input            rxd_i,           // Raw receive data  output           txd_o            // Transmit data to pin);//***************************************************************************// Parameter definitions//***************************************************************************//  parameter //    CLOCK_RATE = 50_000_000,//    DEBOUNCE_TIME = 0.004;    // The switch bounces for 2ms. Use 4ms for safety//  localparam//    CLOCK_PERIOD = 1.0/CLOCK_RATE,//    FILTER       = (DEBOUNCE_TIME + CLOCK_PERIOD/2) / CLOCK_PERIOD;  parameter FILTER = 200_000; // 0.004s at 50MHz    //***************************************************************************// Reg declarations//***************************************************************************//***************************************************************************// Wire declarations//***************************************************************************  wire         lb_sel_filt;          // Filtered value of the lb_sel switch  //***************************************************************************// Code//***************************************************************************  // Instantiate the debouncer.  debouncer #(    .FILTER     (FILTER)  ) debouncer_i0 (    .clk        (clk_tx),    .rst        (rst_clk_tx),    .signal_in  (lb_sel_i),    .signal_out (lb_sel_filt)  );  // Implement the loopback MUX  assign txd_o = lb_sel_filt ? rxd_i : txd_tx;endmodule