Subversion Repositories eco32

//

// tmr.v -- programmable timer

//

`timescale 1ns/10ps

`default_nettype none

module tmr(clk, rst,

           stb, we, addr,

           data_in, data_out,

           ack, irq);

    input clk;

    input rst;

    input stb;

    input we;

    input [3:2] addr;

    input [31:0] data_in;

    output reg [31:0] data_out;

    output ack;

    output irq;

  reg [31:0] counter;

  reg [31:0] divisor;

  reg divisor_loaded;

  reg expired;

  reg alarm;

  reg ien;

  always @(posedge clk) begin

    if (divisor_loaded) begin

      counter <= divisor;

      expired <= 0;

    end else begin

      if (counter == 32'h00000001) begin

        counter <= divisor;

        expired <= 1;

      end else begin

        counter <= counter - 1;

        expired <= 0;

      end

    end

  end

  always @(posedge clk) begin

    if (rst) begin

      divisor <= 32'hFFFFFFFF;

      divisor_loaded <= 1;

      alarm <= 0;

      ien <= 0;

    end else begin

      if (expired) begin

        alarm <= 1;

      end else begin

        if (stb == 1 && we == 1 && addr[3:2] == 2'b00) begin

          // ctrl

          alarm <= data_in[0];

          ien <= data_in[1];

        end

        if (stb == 1 && we == 1 && addr[3:2] == 2'b01) begin

          // divisor

          divisor <= data_in;

          divisor_loaded <= 1;

        end else begin

          divisor_loaded <= 0;

        end

      end

    end

  end

  always @(*) begin

    case (addr[3:2])

      2'b00:

        // ctrl

        data_out = { 28'h0000000, 2'b00, ien, alarm };

      2'b01:

        // divisor

        data_out = divisor;

      2'b10:

        // counter

        data_out = counter;

      2'b11:

        // not used

        data_out = 32'hxxxxxxxx;

      default:

        data_out = 32'hxxxxxxxx;

    endcase

  end

  assign ack = stb;

  assign irq = ien & alarm;

endmodule