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Technical Support On-Line Manuals Cx51 User's Guide ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
sfrThe sfr type defines a special function register (SFR). It is used as follows: sfr name = address; Where
SFRs are declared in the same fashion as other C variables. The only difference is that the type specified is sfr rather than char or int. For example: sfr P0 = 0x80; /* Port-0, address 80h */ sfr P1 = 0x90; /* Port-1, address 90h */ sfr P2 = 0xA0; /* Port-2, address 0A0h */ sfr P3 = 0xB0; /* Port-3, address 0B0h */ P0, P1, P2, and P3 are the SFR name declarations. Names for sfr variables are defined just like other C variable declarations. Any symbolic name may be used in an sfr declaration. The address specification after the equal sign ('=') must be a numeric constant. Expressions with operators are not allowed. Classic 8051 devices support the SFR address range 0x80-0xFF. The NXP 80C51MX provides an additional extended SFR space with the address range 0x180-0x1FF. Note
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