关于“attribute”的应用？

iamchine

查了下Attribute的语法:
{declaration}
attribute AttributeName : TypeName;
{specification}
attribute AttributeName of Name [Signature] : Class is Expression
Signature = [TypeName,...] return TypeName
Class = {either} signal type function architecture {etc}

iamchine

Package p_attr is
      Type t_package_type is (leadless, pin_grid,dip);
       Attribute package_type : t_package_type;    <---- 声明package_type
       Attribute location: integer:                <---- 声明location
    End p_attr;
    Use work.p_attr.all;
    Entity board  is
      Port (…..
              )
    end board;
    architecture cpu_board of board is
      component mc68040
        generic(  );
        port (…..
)
      end component;
    signal a: integer;
    signal b: t_package_type;
    attribute package_type of mc68040 : component is 20; <---这里该是package_type的定义了,但location的呢?而且package_type是个枚举类型的,怎么
赋值为20?不明白
    begin
      a<=mc68040’location;  -- returen 20
      b<=mc68040’package_type;  --return pin_grid;
    end cpu_board;

iamchine

如果按你说的改，倒是对了。也许是书上有错吧？!