从ps/2接口的键盘输入，然后根据接收到的扫描码将输入的键值显示在oHEX0七段译码管。（只实现了数字键0-9的识别）

1 module ps2_keyboard(clk,clrn,ps2_clk,ps2_data,oHEX0);  2     input clk,clrn,ps2_clk,ps2_data;  3     output reg [6:0] oHEX0;  4      5     reg [7:0] data;  6     reg ready;  7     reg overflow; // fifo overflow  8     reg [3:0] count; // count ps2_data bits  9     10 // internal signal, for test 11     reg [9:0] buffer; // ps2_data bits 12     reg [7:0] fifo[7:0]; // data fifo 13     reg [2:0] w_ptr,r_ptr; // fifo write and read pointers 14 // detect falling edge of ps2_clk 15     reg [2:0] ps2_clk_sync; 16     17     //show the input to oHEX0 18     function [6:0] ps2_keyboard_show; 19         input [7:0] key_data; 20         21         begin 22             case (key_data) 23                 8'b00010110 : ps2_keyboard_show = 7'b1111001;//1 24                 8'b00011110 : ps2_keyboard_show = 7'b0100100;//2 25                 8'b00100110 : ps2_keyboard_show = 7'b0110000;//3 26                 8'b00100101 : ps2_keyboard_show = 7'b0011001;//4 27                 8'b00101110 : ps2_keyboard_show = 7'b0010010;//5 28                 8'b00110110 : ps2_keyboard_show = 7'b0000010;//6 29                 8'b00111101 : ps2_keyboard_show = 7'b1111000;//7 30                 8'b00111110 : ps2_keyboard_show = 7'b0000000;//8 31                 8'b01000110 : ps2_keyboard_show = 7'b0010000;//9 32                 8'b01000101 : ps2_keyboard_show = 7'b1000000;//0 33                 default     : ps2_keyboard_show = 7'b1111111;//other input 34             endcase 35         end 36     endfunction 37     38     //detect the falling edge of ps2_clk 39     always @ (posedge clk) 40     begin 41         ps2_clk_sync <= {ps2_clk_sync[1:0],ps2_clk}; 42     end 43     wire sampling = ps2_clk_sync[2] & ~ps2_clk_sync[1];//falling edge:last time 1 this time 0 44 45     always @ (posedge clk) 46     begin 47         if (clrn == 0) // reset 48         begin 49             count <= 0; w_ptr <= 0; r_ptr <= 0; overflow <= 0; 50         end 51         else if (sampling) 52         begin 53             if (count == 4'd10)//10bits 54             begin 55                 if ((buffer[0] == 0) && // start bit 56                     (ps2_data) && // stop bit 57                     (^buffer[9:1])) // odd parity 58                 begin 59                     fifo[w_ptr] <= buffer[8:1]; // kbd scan code 60                     w_ptr <= w_ptr+3'b1; 61                     ready <= 1'b1; 62                     overflow <= overflow | (r_ptr == (w_ptr + 3'b1)); 63                 end 64                 count <= 0; // for next 65             end 66             else 67             begin 68                 buffer[count] <= ps2_data; // store ps2_data 69                 count <= count + 3'b1; 70             end 71         end 72         if ( ready ) // read to output next data 73         begin 74             data = fifo[r_ptr]; 75             r_ptr <= r_ptr + 3'd1; 76             ready <= 1'b0; 77             oHEX0 = ps2_keyboard_show(data); 78         end 79     end 80 endmodule