uart1.v

这个是基于NIOS II的FPGA平台的一个CF卡的接口模块

                                  // outputs:
                                   source_rxd
                                );

  output           source_rxd;
  input   [  9: 0] baud_divisor;
  input            clk;
  input            clk_en;
  input            reset_n;
  input            rx_char_ready;
  input            rxd;

  reg     [  7: 0] d1_stim_data;
  reg              delayed_unxrx_char_readyxx0;
  wire             do_send_stim_data;
  wire             new_rom_pulse;
  wire             pickup_pulse;
  wire             safe;
  wire             source_rxd;
  wire    [  7: 0] stim_data;
  wire             unused_empty;
  wire             unused_overrun;
  wire             unused_ready;

//synthesis translate_off
//////////////// SIMULATION-ONLY CONTENTS
  //stimulus_transmitter, which is an e_instance
  uart1_tx stimulus_transmitter
    (
      .baud_divisor     (baud_divisor),
      .begintransfer    (do_send_stim_data),
      .clk              (clk),
      .clk_en           (clk_en),
      .do_force_break   (1'b0),
      .reset_n          (reset_n),
      .status_wr_strobe (1'b0),
      .tx_data          (d1_stim_data),
      .tx_overrun       (unused_overrun),
      .tx_ready         (unused_ready),
      .tx_shift_empty   (unused_empty),
      .tx_wr_strobe     (1'b1),
      .txd              (source_rxd)
    );

  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          d1_stim_data <= 0;
      else if (do_send_stim_data)
          d1_stim_data <= stim_data;
    end


  //uart1_rx_stimulus_source_character_source_rom, which is an e_drom
  uart1_rx_stimulus_source_character_source_rom_module uart1_rx_stimulus_source_character_source_rom
    (
      .clk       (clk),
      .incr_addr (do_send_stim_data),
      .new_rom   (new_rom_pulse),
      .q         (stim_data),
      .reset_n   (reset_n),
      .safe      (safe)
    );

  //delayed_unxrx_char_readyxx0, which is an e_register
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          delayed_unxrx_char_readyxx0 <= 0;
      else if (clk_en)
          delayed_unxrx_char_readyxx0 <= rx_char_ready;
    end


  assign pickup_pulse = ~(rx_char_ready) &  (delayed_unxrx_char_readyxx0);
  assign do_send_stim_data = (pickup_pulse || new_rom_pulse) && safe;

//////////////// END SIMULATION-ONLY CONTENTS

//synthesis translate_on
//synthesis read_comments_as_HDL on
//  assign source_rxd = rxd;
//synthesis read_comments_as_HDL off


endmodule


module uart1_rx (
                  // inputs:
                   baud_divisor,
                   begintransfer,
                   clk,
                   clk_en,
                   reset_n,
                   rx_rd_strobe,
                   rxd,
                   status_wr_strobe,

                  // outputs:
                   break_detect,
                   framing_error,
                   parity_error,
                   rx_char_ready,
                   rx_data,
                   rx_overrun
                );

  output           break_detect;
  output           framing_error;
  output           parity_error;
  output           rx_char_ready;
  output  [  7: 0] rx_data;
  output           rx_overrun;
  input   [  9: 0] baud_divisor;
  input            begintransfer;
  input            clk;
  input            clk_en;
  input            reset_n;
  input            rx_rd_strobe;
  input            rxd;
  input            status_wr_strobe;

  reg              baud_clk_en;
  wire    [  9: 0] baud_load_value;
  reg     [  9: 0] baud_rate_counter;
  wire             baud_rate_counter_is_zero;
  reg              break_detect;
  reg              d1_source_rxd;
  reg              delayed_unxrx_in_processxx3;
  reg              delayed_unxsync_rxdxx1;
  reg              delayed_unxsync_rxdxx2;
  reg              do_start_rx;
  reg              framing_error;
  wire             got_new_char;
  wire    [  8: 0] half_bit_cell_divisor;
  wire             is_break;
  wire             is_framing_error;
  wire             parity_error;
  wire    [  7: 0] raw_data_in;
  reg              rx_char_ready;
  reg     [  7: 0] rx_data;
  wire             rx_in_process;
  reg              rx_overrun;
  wire             rx_rd_strobe_onset;
  wire             rxd_edge;
  wire             rxd_falling;
  wire    [  9: 0] rxd_shift_reg;
  wire             sample_enable;
  wire             shift_reg_start_bit_n;
  wire             source_rxd;
  wire             stop_bit;
  reg              sync_rxd;
  wire             unused_start_bit;
  wire    [  9: 0] unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_in;
  reg     [  9: 0] unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out;
  uart1_rx_stimulus_source the_uart1_rx_stimulus_source
    (
      .baud_divisor  (baud_divisor),
      .clk           (clk),
      .clk_en        (clk_en),
      .reset_n       (reset_n),
      .rx_char_ready (rx_char_ready),
      .rxd           (rxd),
      .source_rxd    (source_rxd)
    );

  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
        begin
          d1_source_rxd <= 0;
          sync_rxd <= 0;
        end
      else if (clk_en)
        begin
          d1_source_rxd <= source_rxd;
          sync_rxd <= d1_source_rxd;
        end
    end


  //delayed_unxsync_rxdxx1, which is an e_register
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          delayed_unxsync_rxdxx1 <= 0;
      else if (clk_en)
          delayed_unxsync_rxdxx1 <= sync_rxd;
    end


  assign rxd_falling = ~(sync_rxd) &  (delayed_unxsync_rxdxx1);
  //delayed_unxsync_rxdxx2, which is an e_register
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          delayed_unxsync_rxdxx2 <= 0;
      else if (clk_en)
          delayed_unxsync_rxdxx2 <= sync_rxd;
    end


  assign rxd_edge = (sync_rxd) ^  (delayed_unxsync_rxdxx2);
  assign rx_rd_strobe_onset = rx_rd_strobe && begintransfer;
  assign half_bit_cell_divisor = baud_divisor[9 : 1];
  assign baud_load_value = (rxd_edge)? half_bit_cell_divisor :
    baud_divisor;

  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          baud_rate_counter <= 0;
      else if (clk_en)
          if (baud_rate_counter_is_zero || rxd_edge)
              baud_rate_counter <= baud_load_value;
          else 
            baud_rate_counter <= baud_rate_counter - 1;
    end


  assign baud_rate_counter_is_zero = baud_rate_counter == 0;
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          baud_clk_en <= 0;
      else if (clk_en)
          if (rxd_edge)
              baud_clk_en <= 0;
          else 
            baud_clk_en <= baud_rate_counter_is_zero;
    end


  assign sample_enable = baud_clk_en && rx_in_process;
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          do_start_rx <= 0;
      else if (clk_en)
          if (~rx_in_process && rxd_falling)
              do_start_rx <= 1;
          else 
            do_start_rx <= 0;
    end


  assign rx_in_process = shift_reg_start_bit_n;
  assign {stop_bit,
raw_data_in,
unused_start_bit} = rxd_shift_reg;
  assign is_break = ~(|rxd_shift_reg);
  assign is_framing_error = ~stop_bit && ~is_break;
  //delayed_unxrx_in_processxx3, which is an e_register
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          delayed_unxrx_in_processxx3 <= 0;
      else if (clk_en)
          delayed_unxrx_in_processxx3 <= rx_in_process;
    end


  assign got_new_char = ~(rx_in_process) &  (delayed_unxrx_in_processxx3);
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          rx_data <= 0;
      else if (got_new_char)
          rx_data <= raw_data_in;
    end


  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          framing_error <= 0;
      else if (clk_en)
          if (status_wr_strobe)
              framing_error <= 0;
          else if (got_new_char && is_framing_error)
              framing_error <= -1;
    end


  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          break_detect <= 0;
      else if (clk_en)
          if (status_wr_strobe)
              break_detect <= 0;
          else if (got_new_char && is_break)
              break_detect <= -1;
    end


  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          rx_overrun <= 0;
      else if (clk_en)
          if (status_wr_strobe)
              rx_overrun <= 0;
          else if (got_new_char && rx_char_ready)
              rx_overrun <= -1;
    end


  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          rx_char_ready <= 0;
      else if (clk_en)
          if (rx_rd_strobe_onset)
              rx_char_ready <= 0;
          else if (got_new_char)
              rx_char_ready <= -1;
    end


  assign parity_error = 0;
  //_reg, which is an e_register
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out <= 0;
      else if (clk_en)
          unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out <= unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_in;
    end


  assign unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_in = (do_start_rx)? {10{1'b1}} :
    (sample_enable)? {sync_rxd,
    unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out[9 : 1]} :
    unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out;

  assign rxd_shift_reg = unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out;
  assign shift_reg_start_bit_n = unxshiftxrxd_shift_regxshift_reg_start_bit_nxx6_out[0];


endmodule


module uart1_regs (
                    // inputs:
                     address,
                     break_detect,
                     chipselect,
                     clk,
                     clk_en,
                     framing_error,
                     parity_error,
                     read_n,
                     reset_n,
                     rx_char_ready,
                     rx_data,
                     rx_overrun,
                     tx_overrun,
                     tx_ready,
                     tx_shift_empty,
                     write_n,
                     writedata,