sys_pll.v

nios里面用自定义指令集来实现三角函数

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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 sys_pll (
                 // inputs:
                  address,
                  chipselect,
                  clk,
                  read,
                  reset_n,
                  write,
                  writedata,

                 // outputs:
                  c0,
                  c1,
                  readdata,
                  resetrequest
               )
;

  output           c0;
  output           c1;
  output  [ 15: 0] readdata;
  output           resetrequest;
  input   [  2: 0] address;
  input            chipselect;
  input            clk;
  input            read;
  input            reset_n;
  input            write;
  input   [ 15: 0] writedata;

  wire             always_one;
  wire             areset_n;
  wire             c0;
  wire             c1;
  wire             control_reg_en;
  wire    [ 15: 0] control_reg_in;
  reg     [ 15: 0] control_reg_out;
  reg              count_done;
  reg     [  5: 0] countup;
  wire             inclk0;
  reg              not_areset /* synthesis ALTERA_ATTRIBUTE = "PRESERVE_REGISTER=ON"  */;
  wire    [ 15: 0] readdata;
  wire             resetrequest;
  wire    [ 15: 0] status_reg_in;
  reg     [ 15: 0] status_reg_out;
initial
  begin
    countup <= 1'b0;
    count_done <= 1'b0;
    not_areset <= 1'b0;
  end
  assign status_reg_in[15 : 1] = 15'b000000000000000;
  assign resetrequest = ~count_done;
  //Up counter that stops counting when it reaches max value
  always @(posedge clk or negedge areset_n)
    begin
      if (areset_n == 0)
          countup <= 0;
      else if (count_done != 1'b1)
          countup <= countup + 1;
    end


  //Count_done signal, which is also the resetrequest_n
  always @(posedge clk or negedge areset_n)
    begin
      if (areset_n == 0)
          count_done <= 0;
      else if (countup == 6'b111111)
          count_done <= 1'b1;
    end


  //Creates a reset generator that will reset internal counters that are independent of global system reset
  always @(posedge clk or negedge 1'b1)
    begin
      if (1'b1 == 0)
          not_areset <= 0;
      else if (1)
          not_areset <= always_one;
    end


  assign always_one = 1'b1;
  assign status_reg_in[0] = 1'b0;
  assign areset_n = not_areset;
  assign inclk0 = clk;
  //Mux status and control registers to the readdata output using address as select
  assign readdata = (address[0] == 0)? status_reg_out :
    ({control_reg_out[15 : 2], ~control_reg_out[1], control_reg_out[0]} );

  //Status register - Read-Only
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          status_reg_out <= 0;
      else if (1'b1)
          status_reg_out <= status_reg_in;
    end


  //Control register - R/W
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          control_reg_out <= 0;
      else if (control_reg_en)
          control_reg_out <= {control_reg_in[15 : 2], ~control_reg_in[1], control_reg_in[0]};
    end


  assign control_reg_in = writedata;
  assign control_reg_en = (address == 3'b001) && write && chipselect;
  //s1, which is an e_avalon_slave
  altpllsys_pll the_pll
    (
      .c0 (c0),
      .c1 (c1),
      .inclk0 (inclk0)
    );



endmodule