非同于MCU的獨(dú)立按鍵消抖動

module key_scan

#(

parameter KEY_WIDTH = 2

)

(

input clk, //50MHz

input rst_n,

input [KEY_WIDTH-1:0] key_data,

output key_flag,

output reg [KEY_WIDTH-1:0] key_value

);

//---------------------------------

//escape the jitters

reg [19:0] key_cnt; //scan counter

reg [KEY_WIDTH-1:0] key_data_r;

always @(posedge clk or negedge rst_n)

begin

if(!rst_n)

begin

key_data_r = {KEY_WIDTH{1'b1}};

key_cnt = 0;

end

else

begin

key_data_r = key_data; //lock the key value

if((key_data == key_data_r) (key_data != {KEY_WIDTH{1'b1}})) //20ms escape jitter

begin

if(key_cnt 20'hfffff)

key_cnt = key_cnt + 1'b1;

end

else key_cnt = 0;

end

end

wire cnt_flag = (key_cnt == 20'hffffe) ? 1'b1 : 1'b0;//!!

//-----------------------------------

//sure the key is pressed

reg key_flag_r;

always@(posedge clk or negedge rst_n)

begin

if(!rst_n)

begin

key_flag_r = 0;

key_value = 0;

end

else if(cnt_flag)

begin

key_flag_r = 1;

key_value = key_data; //locked the data

end

else //let go your hand

key_flag_r = 0; //lock the key_value

end

//---------------------------------------

//Capture the rising endge of the key_flag

reg key_flag_r0,key_flag_r1;

always@(posedge clk or negedge rst_n)

begin

if(!rst_n)

begin

key_flag_r0 = 0;

key_flag_r1 = 0;

end

else

begin

key_flag_r0 = key_flag_r;

key_flag_r1 = key_flag_r0;

end

end

assign key_flag = ~key_flag_r1 key_flag_r0;

endmodule