iamzhr

 if (Slk'event and Slk='1') then
     elsif CS='1' then   
        shift_buf<=shl(shift_buf,"1");
        shift_buf(0)<='0';
       end if;

第一行的then后面怎么没有语句啊，语法不对啊，据我对你程序的理解应该改成

if (Slk'event and Slk='０') then
     if CS='1' then   
        shift_buf<=shl(shift_buf,"1");
        shift_buf(0)<='0';
       end if;

end if;