Ada语言位域指定
我们先贴一段代码：
-- IO地址:WORD型与对应[站号-卡号-通道号]
type IO_Address(T:Boolean:=True) is record
case T is
when True=>
Addr:word;
when False=>
Station:Bit4;
Card :Bit4;
IO :byte;
end case;
end record with Unchecked_Union;
for IO_ADDRESS use record
at mod 2;
Addr at 0 range 0..15;
Station at 0 range 12..15;
Card at 0 range 8..11;
IO at 0 range 0..7;
end record;
for IO_ADDRESS'size use 16;
这里需要对指定中的at和range进行说明，
AT 从本结构第几个字节开始（初始序标为0） RANGE 从开始字节的第N0（比特）位到第N1个（比特）位。