switch_pio.v

DE2开发板上的资料,主要是他的例子,含有各种接口程序,如VGA,USB,LCD等

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// synthesis translate_off
`timescale 1ns / 1ps
// synthesis translate_on

// turn off superfluous verilog processor warnings 
// altera message_level Level1 
// altera message_off 10034 10035 10036 10037 10230 10240 10030 

module switch_pio (
                    // inputs:
                     address,
                     clk,
                     in_port,
                     reset_n,

                    // outputs:
                     readdata
                  )
;

  output  [ 17: 0] readdata;
  input   [  1: 0] address;
  input            clk;
  input   [ 17: 0] in_port;
  input            reset_n;

  wire             clk_en;
  wire    [ 17: 0] data_in;
  wire    [ 17: 0] read_mux_out;
  reg     [ 17: 0] readdata;
  assign clk_en = 1;
  //s1, which is an e_avalon_slave
  assign read_mux_out = {18 {(address == 0)}} & data_in;
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          readdata <= 0;
      else if (clk_en)
          readdata <= read_mux_out;
    end


  assign data_in = in_port;

endmodule