使用Verilog HDL 实现图11-28 所示的4*4 矩阵键盘的接口扫描模块。
代码语言：js复制module button_scan(
clk,in,out,num
);
input clk;
input [3:0]in;
output [3:0]out;
output [4:0]num;
reg [4:0]num;
reg [1:0]cnt=0;
reg [1:0]tmp=0;
reg [3:0]out_reg=0;
wire [7:0]dsample;
assign dsample={out_reg,in};
assign out=out_reg;
//generate the column of martix
always @ ( posedge clk )
begin
cnt<=cnt 1;
case(cnt)
0:out_reg<=4'b1000;
1:out_reg<=4'b0100;
2:out_reg<=4'b0010;
3:out_reg<=4'b0001;
endcase
end
//get the key number
always @ ( posedge clk )
begin
if(in==4'b0000)
begin
if(tmp==3)
begin
num<=16;
tmp<=0;
end
else
begin
num<=num;
tmp<=tmp 1;
end
end
else
begin
tmp<=0;
case(dsample)
8'b1000_0001 : num <= 0;
8'b1000_0010 : num <= 1;
8'b1000_0100 : num <= 2;
8'b1000_1000 : num <= 3;
8'b0100_0001 : num <= 4;
8'b0100_0010 : num <= 5;
8'b0100_0100 : num <= 6;
8'b0100_1000 : num <= 7;
8'b0010_0001 : num <= 8;
8'b0010_0010 : num <= 9;
8'b0010_0100 : num <= 10;
8'b0010_1000 : num <= 11;
8'b0001_0001 : num <= 12;
8'b0001_0010 : num <= 13;
8'b0001_0100 : num <= 14;
8'b0001_1000 : num <= 15;
endcase
end
end
endmodule
