Uart.v

   1 `define IN_CLK 8388608
   2 `define OUT_CLK 9600
   3 `define CLK_DIV `IN_CLK / `OUT_CLK
   4 `define MMAP_ADDR 16'hFF50
   5
   6 module UART(
   7         input clk,
   8         input wr,
   9         input rd,
  10         input [15:0] addr,
  11         input [7:0] data,
  12         output reg serial);
  13
  14         reg [7:0] data_stor = 0;
  15         reg [15:0] clkdiv = 0;
  16         reg have_data = 0;
  17         reg data_end = 0;
  18         reg [3:0] diqing = 4'b0000;
  19
  20         wire new = (wr) && (!have_data) && (addr == `MMAP_ADDR);
  21
  22         always @ (negedge clk)
  23         begin
  24                 /* deal with diqing */
  25                 if(new) begin
  26                         data_stor <= data;
  27                         have_data <= 1;
  28                         diqing <= 4'b0000;
  29                 end else if (clkdiv == 0) begin
  30                         diqing <= diqing + 1;
  31                         if (have_data)
  32                                 case (diqing)
  33                                 4'b0000: serial <= 0;
  34                                 4'b0001: serial <= data_stor[0];
  35                                 4'b0010: serial <= data_stor[1];
  36                                 4'b0011: serial <= data_stor[2];
  37                                 4'b0100: serial <= data_stor[3];
  38                                 4'b0101: serial <= data_stor[4];
  39                                 4'b0110: serial <= data_stor[5];
  40                                 4'b0111: serial <= data_stor[6];
  41                                 4'b1000: serial <= data_stor[7];
  42                                 4'b1001: serial <= 1;
  43                                 4'b1010: have_data <= 0;
  44                                 default: $stop;
  45                         endcase
  46                 end
  47
  48                 /* deal with clkdiv */
  49                 if((new && !have_data) || clkdiv == `CLK_DIV)
  50                         clkdiv <= 0;
  51                 else
  52                         clkdiv <= clkdiv + 1;
  53         end
  54 endmodule