Subversion Repositories ps2_host_controller

//////////////////////////////////////////////////////////////////////

////                                                              ////

////  ps2_host_tx.v                                               ////

////                                                              ////

////  Description                                                 ////

////  Transmitter part, sending bits down the ps2_data line       ////

////                                                              ////

////  Author:                                                     ////

////      - Piotr Foltyn, piotr.foltyn@gmail.com                  ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2011 Author                                    ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source is distributed in the hope that it will be       ////

//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////

//// PURPOSE.  See the GNU Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

module ps2_host_tx(

  input  wire sys_clk,

  input  wire sys_rst,

  input  wire ps2_clk_posedge,

  inout  wire ps2_data,

  input  wire [7:0] tx_data,

  input  wire send_req,

  output wire busy

);

reg [11:0] frame;

wire frame_is_zero = ~|frame;

always @(posedge sys_clk)

begin

  if (sys_rst | (~send_req & frame_is_zero)) begin

    frame <= 0;

  end

  else if (frame_is_zero) begin

    frame <= {2'b00, tx_data[0], tx_data[1], tx_data[2], tx_data[3],

                     tx_data[4], tx_data[5], tx_data[6], tx_data[7], ~^tx_data, 1'b1};

  end

  else begin

    frame <= (ps2_clk_posedge) ? {frame[10:0], 1'b0} : frame;

  end

end

// Send data down the line.

assign ps2_data = ((~|frame[10:0]) | frame[0]) ? 1'bz : frame[11];

// Keep high until all bits transmitted and ACK received

assign busy = ~frame_is_zero;

endmodule