1. 4*4键盘的结构为4行4列，共16个交叉点，代表16个按键，行编号为A，列编号为B。按下某键后，辨别和读取键值一般采用如下方法：
向A端口扫描输入一组只含有一个0的4位数据，若有按键按下，B端口会输出相应的数据，然后结合A、B端口的数据，判断按键的位置。
2. 整个键盘扫描检测，设计思想还是编码译码。扫描时钟用1KHz，用一个模4的计数器，每个计数值对应一行，编码A。组合读入的列编码，
根据查找表，就很容易确定按键位置，按键值。
3. 4*4矩阵键盘扫描检测程序：
1 /*4*4 keyboard scan and display */
2 //2020-11-04
3 //by YongFengXie
4 module key4x4(rst,clk50M,a,b,led7s);
5 input clk50M; //keyboard scan clock
6 input rst;
7 input [3:0] b;
8 output reg [3:0] a; // output scan signal to keyboard
9 output reg [6:0] led7s;
10 reg [3:0] keyvalue;
11 reg [1:0] q; //counter 4
12 reg clk; // 1KHz
13 reg [14:0] count; //div counter,50M to 1K
14
15 always @(posedge rst or posedge clk50M)
16 // 50M divide 25 000 to 1K Hz
17 begin
18 if(rst)
19 begin
20 clk <= 0;
21 count <= 0;
22 q<=0;
23 end
24 else if(count == 25000)
25 begin
26 count <= 0;
27 clk <= ~clk;
28 end
29 else
30 count <= count + 1;
31 end
32
33 always @(posedge clk)
34 begin
35 q <= q+1;
36 case(q) // send data to keyboard A port
37 0: a<=4'b1110;
38 1: a<=4'b1101;
39 2: a<=4'b1011;
40 3: a<=4'b0111;
41 default: a<=4'b0000;
42 endcase
43 case({a,b}) // judge keyvalue
44 8'b1110_0111: begin keyvalue<=4'b0000;
45 led7s<=7'b1000000;
46 end // key0
47 8'b1110_1011: begin keyvalue<=4'b0001;
48 led7s<=7'b1111001;
49 end // key1
50 8'b1110_1101: begin keyvalue<=4'b0010;
51 led7s<=7'b0100100;
52 end // key2
53 8'b1110_1110: begin keyvalue<=4'b0011;
54 led7s<=7'b0110000;
55 end // key3
56 8'b1101_0111: begin keyvalue<=4'b0100;
57 led7s<=7'b0011001;
58 end // key4
59 8'b1101_1011: begin keyvalue<=4'b0101;
60 led7s<=7'b0010010;
61 end // key5
62 8'b1101_1101: begin keyvalue<=4'b0110;
63 led7s<=7'b0000010;
64 end // key6
65 8'b1101_1110: begin keyvalue<=4'b0111;
66 led7s<=7'b1111000;
67 end // key7
68 8'b1011_0111: begin keyvalue<=4'b1000;
69 led7s<=7'b0000000;
70 end // key8
71 8'b1011_1011: begin keyvalue<=4'b1001;
72 led7s<=7'b0010000;
73 end // key9
74 8'b1011_1101: begin keyvalue<=4'b1010;
75 led7s<=7'b0001000;
76 end // keyA
77 8'b1011_1110: begin keyvalue<=4'b1011;
78 led7s<=7'b0000011;
79 end // keyB
80 8'b0111_0111: begin keyvalue<=4'b1100;
81 led7s<=7'b1000110;
82 end // keyC
83 8'b0111_1011: begin keyvalue<=4'b1101;
84 led7s<=7'b0100001;
85 end // keyD
86 8'b1110_1101: begin keyvalue<=4'b1110;
87 led7s<=7'b0000110;
88 end // keyE
89 8'b0111_1110: begin keyvalue<=4'b1111;
90 led7s<=7'b0001110;
91 end // keyF
92 default:begin keyvalue<=4'b0000;led7s<=7'b1111111;end
93 endcase
94 end
95
96 endmodule
97
98
99测试代码：
1 /*4*4 keyboard scan and display testbench */
2 //2020-11-04
3 //by YongFengXie
4 `timescale 10ns/1ns
5 module key4x4_tb;
6 reg clk50M; //keyboard scan clock
7 reg rst;
8 reg [3:0] b;
9 wire [3:0] a; // output scan signal to keyboard
10 wire [6:0] led7s;
11
12 key4x4 ub(rst,clk50M,a,b,led7s);
13
14 initial begin
15 clk50M=0;
16 rst=1;
17 b=4'b0000;
18 #2 rst=0;
19 #1600000 $stop;
20 end
21
22 always #1 clk50M=~clk50M;
23
24 initial begin #100000 b=4'b0111;
25 #100000 b=4'b1011;
26 #100000 b=4'b1101;
27 #100000 b=4'b1110;
28 end
29
30 endmodule仿真结果：
4. 总结：
参照王金明的设计，其实还是有很多问题：1。矩阵键盘需要淘；2。仿真因为包含分频，所以测试模块还不完善，16个按键，16种组合，每种持续时长都是需要考虑。
