adc_pio.v

nios 嵌入式系统基础教程配套实验 定制基于AVALON总线的用户外设实验

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// synthesis translate_off
`timescale 1ns / 100ps
// synthesis translate_on
module adc_pio (
                 // inputs:
                  address,
                  chipselect,
                  clk,
                  reset_n,
                  write_n,
                  writedata,

                 // outputs:
                  bidir_port,
                  readdata
               );

  inout   [  2: 0] bidir_port;
  output  [  2: 0] readdata;
  input   [  1: 0] address;
  input            chipselect;
  input            clk;
  input            reset_n;
  input            write_n;
  input   [  2: 0] writedata;

  wire    [  2: 0] bidir_port;
  wire             clk_en;
  reg     [  2: 0] data_dir;
  wire    [  2: 0] data_in;
  reg     [  2: 0] data_out;
  wire    [  2: 0] read_mux_out;
  reg     [  2: 0] readdata;
  assign clk_en = 1;
  //s1, which is an e_avalon_slave
  assign read_mux_out = ({3 {(address == 0)}} & data_in) |
    ({3 {(address == 1)}} & data_dir);

  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          readdata <= 0;
      else if (clk_en)
          readdata <= read_mux_out;
    end


  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          data_out <= 0;
      else if (chipselect && ~write_n && (address == 0))
          data_out <= writedata[2 : 0];
    end


  assign bidir_port[0] = data_dir[0] ? data_out[0] : 1'bZ;
  assign bidir_port[1] = data_dir[1] ? data_out[1] : 1'bZ;
  assign bidir_port[2] = data_dir[2] ? data_out[2] : 1'bZ;
  assign data_in = bidir_port;
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          data_dir <= 0;
      else if (chipselect && ~write_n && (address == 1))
          data_dir <= writedata[2 : 0];
    end




endmodule