module jiou(ain,out,key1,key2,clk);
input clk;
input key1,key2;
input [6:0]ain;
output [7:0]out
reg clk1;
reg [7:0]out;
reg keya1,keyb1,keya2,keyb2;
parameter i1=49;
parameter i2=99;
reg [7:0]t1,t2;
reg k;
reg [8:0]f;
reg a1,b1;
reg [7:0]c2;
always @(posedge clk)begin
if(t1<=i1) t1<=t1+1;
else t1<=0;
if(t1==i1) k<=k+1;end
always @(posedge k)begin
if(t2<=i2) t2<=t2+1;
else t2<=0;
if(t2==i2) clk1<=clk1+1;end
always@(posedge clk)
begin
keya1<=key1;
keyb1<=key2;
a1<=keya1^key1;
b1<=keyb1^key2;
end
always@(posedge clk1)
begin
if(f<200)
f<=f+1;
else f<=f+1;
if(f==200 & a1)
keya2<=key1;
else
keya2<=key1;
if(f==200 & b1)
keyb2<=key2;
else
keyb2<=keyb1;
end
always@(posedge clk)
begin
c2<=0;
if(keya2)
begin
c2<=^ain;
if(keyb2)
out<={~c2[0],ain};
else
out<={c2[0],ain};
end
else
out<=0;
end
endmodule
中的begin
keya1<=key1;
keyb1<=key2;
a1<=keya1^key1;
b1<=keyb1^key2;
end
是什么意思啊？I