C语言控制51单片机 sbit 与 sfr 的用法（keil扩展指令 ）

（keil 中 help 的说明）

Arguments sbit sfr_symbol = bit-address;

Description The sbit statement defines a special function register bit:

Where

*sfr_symbol is the name of the Special Function Register (SFR) symbol to define. bit-address is the address of the SFR bit in the format address^bit_position.*

The sbit statement allows you to define SFR bit data in a consistent manner with the Cx51 compiler. With this statement you may use a generic SFR register definition file for the Cx51 compiler and the Ax51 assembler.

Example sbit P0_0 = P0^0; sbit P0_1 = 0x90^1;

sbit 用于特殊功能寄存器中可位寻址的位地址。类似于C语言中的宏定义，对选定位地址进行某特殊功能的命名。

格式为：sbit 命名功能 = 位地址

Arguments sfr sfr_symbol = address;

Description The sfr statement defines a special function register:

*sfr_symbol is the name of the Special Function Register (SFR) symbol to define. address is the address of the SFR.*

The sfr statement allows you to define SFR data in a consistent manner with the Cx51 compiler. With this statement you may use a generic SFR register definition file for the Cx51 compiler and the Ax51 assembler.

Example sfr P0 = 0x80; sfr P1 = 0x90;

sfr 定义特殊功能寄存器中的字节。类似于C语言中的宏定义，对选定字节地址进行某特殊功能的命名。

格式为：sfr 功能命名 = 地址（位地址首位）

1）位寻址区 字节地址范围为 20H~2FH， 这16个单元（共计128位）的每一位都有一个对应位地址， 位地址范围为 00H~7FH。

2）SFR区 字节地址范围为80H~FFH， 字节地址30H~7FH为数据缓冲区，用户RAM区， 位地址范围紧接上述位寻址区位地址范围，SFR区位地址范围为 80H~FFH。