song.v

verilog 经典例子的源码 非常适用于初学verilog的朋友们

module song(clk_6MHz,clk_4Hz,speaker,high,med,low);
input clk_6MHz, clk_4Hz;
output speaker;
output[3:0] high,med,low;
reg[3:0] high,med,low;
reg[13:0] divider,origin;
reg[7:0] counter;
reg speaker;
wire carry;

assign carry=(divider==16383);

always @(posedge clk_6MHz)
begin
if(carry)  	divider=origin;
else  		divider=divider+1;
end

always @(posedge carry)
begin
speaker=~speaker;
end

always @(posedge clk_4Hz)
  begin
case({high,med,low})
'b000000000011:	origin=7281;
'b000000000101:	origin=8730;
'b000000000110:	origin=9565;
'b000000000111:	origin=10310;
'b000000010000:	origin=10647;
'b000000100000:	origin=11272;
'b000000110000:	origin=11831;
'b000001010000:	origin=12556;
'b000001100000:	origin=12974;
'b000100000000:	origin=13516;
'b000000000000:	origin=16383;
endcase
  end

always @(posedge clk_4Hz)
  begin
if(counter==63) counter=0;
else 		counter=counter+1;
case(counter)
0:	{high,med,low}='b000000000011;
1:	{high,med,low}='b000000000011;
2:	{high,med,low}='b000000000011;
3:	{high,med,low}='b000000000011;
4:	{high,med,low}='b000000000101;
5:	{high,med,low}='b000000000101;
6:	{high,med,low}='b000000000101;
7:	{high,med,low}='b000000000110;
8:	{high,med,low}='b000000010000;
9:	{high,med,low}='b000000010000;
10:	{high,med,low}='b000000010000;
11:	{high,med,low}='b000000100000;
12:	{high,med,low}='b000000000110;
13:	{high,med,low}='b000000010000;
14:	{high,med,low}='b000000000101;
15:	{high,med,low}='b000000000101;

16:	{high,med,low}='b000001010000;
17:	{high,med,low}='b000001010000;
18:	{high,med,low}='b000001010000;
19:	{high,med,low}='b000100000000;
20:	{high,med,low}='b000001100000;
21:	{high,med,low}='b000001010000;
22:	{high,med,low}='b000000110000;
23:	{high,med,low}='b000001010000;
24:	{high,med,low}='b000000100000;
25:	{high,med,low}='b000000100000;
26:	{high,med,low}='b000000100000;
27:	{high,med,low}='b000000100000;
28:	{high,med,low}='b000000100000;
29:	{high,med,low}='b000000100000;
30:	{high,med,low}='b000000100000;
31:	{high,med,low}='b000000100000;
	
32:	{high,med,low}='b000000100000;
33:	{high,med,low}='b000000100000;
34:	{high,med,low}='b000000100000;
35:	{high,med,low}='b000000110000;
36:	{high,med,low}='b000000000111;
37:	{high,med,low}='b000000000111;
38:	{high,med,low}='b000000000110;
39:	{high,med,low}='b000000000110;
40:	{high,med,low}='b000000000101;
41:	{high,med,low}='b000000000101;
42:	{high,med,low}='b000000000101;
43:	{high,med,low}='b000000000110;
44:	{high,med,low}='b000000010000;
45:	{high,med,low}='b000000010000;
46:	{high,med,low}='b000000100000;
47:	{high,med,low}='b000000100000;
	
48:	{high,med,low}='b000000000011;
49:	{high,med,low}='b000000000011;				
50:	{high,med,low}='b000000010000;
51:	{high,med,low}='b000000010000;
52:	{high,med,low}='b000000000110;
53:	{high,med,low}='b000000000101;
54:	{high,med,low}='b000000000110;
55:	{high,med,low}='b000000010000;
56:	{high,med,low}='b000000000101;
57:	{high,med,low}='b000000000101;
58:	{high,med,low}='b000000000101;	
59:	{high,med,low}='b000000000101;
60:	{high,med,low}='b000000000101;
61:	{high,med,low}='b000000000101;
62:	{high,med,low}='b000000000101;
63:	{high,med,low}='b000000000101;
endcase
end
endmodule