新建 文本文档.txt

自己编写的8254计数器／计时器

 when "01"  =>
     case  mode_choice is 
         when "000" => --mode0
    out_sgnl(1) <=mode0(clk,mode0_start,gate(1),CE1); 
        when "001" => --mode1
           out_sgnl(1)<=mode1(clk,gate(1),mode1_start,ce1);
        when "X10" =>
           out_sgnl(1)<=mode2(clk,gate(1),mode2_start,ce1);
       when "X11"   =>
            out_sgnl(1)<=mode3(clk,gate(1),mode3_start,ce1);
       when "100" =>
            out_sgnl(1)<=mode4(clk,gate(1),mode4_start,ce1);
       when "101" =>
             out_sgnl(1)<=mode5(clk,gate(1),mode5_start,ce1);
     when others => null;
   end case ;
when "10"  =>
     case  mode_choice is 
        when "000" => --mode0
         out_sgnl(2) <=mode0(clk,gate(2),mode0_start,CE2); 
        when "001" => --mode1
           out_sgnl(2)<=mode1(clk,gate(2),mode1_start,ce2);
        when "X10" =>
           out_sgnl(2)<=mode2(clk,gate(2),mode2_start,ce2);
       when "X11"   =>
            out_sgnl(2)<=mode3(clk,gate(2),mode3_start,ce2);
       when "100" =>
            out_sgnl(2)<=mode4(clk,gate(2),mode4_start,ce2);
       when "101" =>
             out_sgnl(2)<=mode5(clk,gate(2),mode5_start,ce2);
       when others => null;
    end case;
if( mode4_start='1' and gate='1') then  
     if (cee=5)  then
         tmp4:='0';
            cee:=0;
         else  
         
       cee:=cee+1;
       tmp4:='1';
         end if;
  elsif (mode4_start='1' and gate='0') then 
        cee:=0;
     end if;