month_c.v.bak

用vierilog语言描写的电子时钟源码

//BCD计数器，从0计到0x99(BCD)
module	month_c(reset,clk,monthnum,yearstyle,q,cout);
input		reset,clk,yearstyle;
input [7:0] monthnum;
output cout;
output	[7:0]	q;

reg cout;
reg		[7:0]	q,length;


always	@(posedge clk or negedge reset)
  begin
  if(!reset)	
    q<=8'd1;	
    cout<=0;
  else begin
     begin
      if(monthnum==8'b1||monthnum==8'b11||monthnum==8'b101||monthnum==8'b111||monthnum==8'b1000||monthnum==8'b10000||monthnum==8'b10010)
        length=8'd49;
     else if(monthnum==8'b100||monthnum==8'b110||monthnum==8'b1001||monthnum==8'b10001)
        length=8'd48;
     else 
        begin
          if(yearstyle)
            length=8'd40;
          else length=8'd41; 
        end 
     end
  begin
       if(((monthnum==8'b100||monthnum==8'b110||monthnum==8'b1001||monthnum==8'b10001)&&q==8'd49))
         begin
           cout<=0;
           q<=8'd48;
         end
       else  if(monthnum==8'b10&&yearstyle&&q>8'd40)
         begin
           cout<=0;
           q<=8'd40;
         end
       else  if(monthnum==8'b10&&(!yearstyle)&&q>8'd41)
         begin
           cout<=0;
           q<=8'd41;
         end
       else if(q==length)
         begin		
           q<=8'd1 ;
           cout<=1;
         end
	    else
         begin
	        cout<=0;
           if(q[3:0]==4'd9)
             begin					//bcd formt
               q[3:0]<=4'd0;
		         q[7:4]<=q[7:4]+1;
	           end
	        else
	            q<=q+1;
	       end
      end
  end     
  end
endmodule