计数器

module yinsong (RST,CLK,CNT);
input RST, CLK;
output [3:0] CNT;
reg [3:0] CNT;
integer CNT_MAX = 6;       
always @ (posedge CLK or posedge RST) 
begin
  if(RST) 
    CNT = 0;               
  else if(CNT < CNT_MAX)   
    begin
        CNT = CNT + 1'b1;
    end
  else                    
    begin
        CNT = 0;
        if(CNT_MAX < 9)
            CNT_MAX = CNT_MAX + 1;
        else
            CNT_MAX = 6;
    end
end
endmodule