VHDL 的错误和解决集总

    Error (10465): VHDL error at jce.vhd(34): name "present_state" cannot be used because it is already used for a previously declared item
Error (10476): VHDL error at jce.vhd(34): type of identifier "s7" does not agree with its usage as " void" type
Error: Quartus II Analysis & Synthesis was unsuccessful. 2 errors, 0 warnings
 

 

   首先点击错误进行定位————发现type of identifier "s7" does not agree with its usage as " void" type （s7变量和viod类型不匹配。）

   仔细观察，很容易发现错误的原因。是“

        if datain='1' then

          present_state:s7;（就是此种错误容易引发其他类型的错误产生，如it is already used for a previously declared item——系统提示的错误（但不是错误的根源））
          else

             present_state:=s1;end if; 

          更正是present_state:=s7;（一个等号引发的“血案”）

  

 

      再编译一下问题解决！！！

 类似，像出现定义错误之类的问题-----可能不是问题和警告的本身。而是要找到真正的错误，如错误边的语句语法错误或者变量字母是否出错！

 

 

 

      所以，上述的错误很容易产生，解决问题，关键是从系统所提示的错误找到根源！！！

 

 

  待续ing.......