谁能讲解一下IAR STM8 1.3头文件io_macros.h这段程序

谁能讲解一下IAR STM8 1.3头文件io_macros.h这段程序：
/*---------------------------------------------
* Define NAME as an I/O 8 bit reg
* Access of 8 bit reg:  NAME
*--------------------------------------------*/
#define __IO_REG8(NAME, ADDRESS, ATTRIBUTE)              \
                  __near __no_init volatile ATTRIBUTE unsigned char NAME @ ADDRESS;

/*---------------------------------------------
* Define NAME as an I/O reg with bit accesss
* Access of 8 bit reg:  NAME
* Access of bit(s):     NAME_bit.noXX
*--------------------------------------------*/
#define __IO_REG8_BIT(NAME, ADDRESS, ATTRIBUTE, BIT_STRUCT)       \
                      __near __no_init volatile ATTRIBUTE union   \
                        {                                         \
                          unsigned char NAME;                     \
                          BIT_STRUCT NAME ## _bit;                \
                        } @ ADDRESS;

#endif /* __IAR_SYSTEMS_ICC__ */

回答1：

将名字为NAME的寄存器定义在地址ADDRESS，指定属性为ATTRIBUTE(比如只读，读写等等)

第二个定义和第一个的不同在于这个寄存器可以进行位操作

使用这个2个定义后就可以使用
__IO_REG8(NAME, ADDRESS, ATTRIBUTE)
简短的代替下面一串
__near __no_init volatile ATTRIBUTE unsigned char NAME @ ADDRESS;

十分简单明了

补充：

__near __no_init
这些是特定编译器支持的关键字.....