跪求各位大仙帮看看 问题出在哪里呀？

此为程序
  

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
entity  cal_test  is
port (rowut std_logic_vector(3 downto 0);

col:in  std_logic_vector(3 downto 0);
      flhz:in std_logic;
      rst:in std_logic;
c0ut std_logic_vector(3 downto 0);
c1ut std_logic_vector(3 downto 0);
c2ut std_logic_vector(3 downto 0)
      );
end cal_test;
architecture beh of cal_test  is
  type state_type  is (s0,s1,s2,s3,s4);
signal  state : state_type;
signal  d,d0,d1,d2,d3,d_reg:std_logic_vector(4 downto 0);
signal      op :  std_logic_vector(1 downto 0);
signal  a:std_logic_vector(7 downto 0);
signal datac, datal, datah:std_logic_vector(3 downto 0);
begin
d<=d0 or d1 or d2 or d3;
process(flhz, rst)
    begin
if (rst='1') then
state<=s0;
datal<="0000";
datah<="1011";
datac<="1011";
row<="1110";
elsif (flhz' event and flhz='1') then
case state is
when s0=>   
      case col is
      when "1110" => d0 <="10000";
      when "1101" => d0 <="10100";
      when "1011" => d0 <="11000";
      when "0111" => d0 <="11100";
      when others => d0 <="00000";
      end case;
      row<="1101";
      state<=s1;

when s1=>        
     case col is
     when "1110" => d1 <="10001";
     when "1101" => d1 <="10101";
     when "1011" => d1 <="11001";
     when "0111" => d1 <="11101";
     when  others=> d1 <="00000";
end case;
state<=s2;
row<="1011";

when  s2=>            
     case col is
     when "1110" => d2 <="10010";
     when "1101" => d2 <="10110";
     when "1011" => d2 <="11010";
     when "0111" => d2 <="11110";
     when  others=> d2 <="00000";
     end case;
     state<=s3;
     row<="1011";

when s3=>state<=s4;   
     case col is
     when "1110" => d3 <="10011";
     when "1101" => d3 <="10111";
     when "1011" => d3 <="11011";
     when "0111" => d3 <="11111";
     when  others=> d3 <="00000";
     end case;

when s4=> row <="1110";
state<=s0;
if (d/=d_reg) then
  d_reg<=d;
if ((d<="11001") and (d>="10000"))then
datah<=datal;
datal<=d(3 downto 0);

elsif (d="11010") then
     op<="01";   
     a<=datah&datal;
     datah<="0000";
     datal<="0000";
elsif (d="11011")  then
    op<="10";   
    a<=datah & datal;
datah<="0000";
datal<="0000";
elsif(d="11100") then  
    datal<="0000";
datah<="1011";
datac<="1011";
elsif (d="1111")  then  

   
case op is
when "01" =>if((a (3 downto 0)+datal)<="1001" and (a(3 downto 0)+datal) >=a(3 downto 0))         
    then
    datal<=a(3 downto 0)+datal;
    if((a (7 downto 4)+datah)<="1001" and (a(7 downto 4)+datah)>=a(7 downto 4))
    then
     datah<=a(7 downto 4)+datah;
datac<="0001";
  else
    datah<=a(7 downto 4)+datah;
    datac<="0001";
    end if;
else
datal<=a(3 downto 0)+datal+"0110";
if((a (7 downto 4)+datah+"0001"))<="1001" and (a(7 downto 4)+datah+"0001">a(7 downto 4))  then
  datah<=a(7 downto 4)+datah+"0001";
    datac<="1011";
else
     datah<=a(7 downto 4)+datah+"0110"+"0001";
     datac<="0001";
  end if;
end if;
            when "10"=> if(a<datah&datal) then  
             datac<="1010";

           if (a (3 downto 0) >datal) then
              datal<=datal+"1010"-a(3 downto 0);
              datah<=datah-"0001"-a(7 downto 4);
else
    datal<=datal-a(3 downto 0);
    datah<=datah-a(7 downto 4);
  end if;
else
    datac<="1011";
   if (a(3 downto 0)<datal) then
datal<=a(3  downto  0)+"1010"-datal;
      datah<=a(7 downto 4 )-"0001"-datah;
    else
        datal<=a(3 downto 0)-datal;
        datah<=a(7 downto 4)-datah;
    end if;
  end if;
when others=>null;
end case;
end if;
  end if;
end case;
c0<=datal;
c1<=datah;
c2<=datac;
end if;
end process;
end beh;