mcs-51单片机的位寻址地址内部RAM区从字节地址20H-2FH(16个字节可以位寻址）位地址00H-7FH特殊功能寄存器字节地址80H88H90H98H---F0HF8H(16个字节可以位寻址）位地址80H-FFH
