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Special Function Registers

The 251 family of microcontrollers provides a distinct memory area for accessing Special Function Registers (SFRs). SFRs are used in your program to control timers, counters, serial I/Os, port I/Os, and peripherals. SFRs reside from address 0x80 to 0xFF and can be accessed as bits, bytes, and words. For more information about Special Function Registers, refer to the Intel 251/930 Embedded Controllers data book or other 251 data books.

Within the 251 family, the number and type of SFRs vary. Note that no SFR names are predefined by the C251 Compiler. However, declarations for SFRs are provided in include files.

The C251 Compiler provides a number of include files for various 251 derivatives. Each file contains declarations for the SFRs available on that derivative. Refer to 251 Special Function Register Include Files for more information about include files.

The C251 Compiler provides access to SFRs with the sfr, sfr16, and sbit data types.

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