C51: Locate struct to SFR Space

Information in this article applies to:

• C51 All Versions

QUESTION

Is there a way to locate a C struct into the 8051's SFR (Special Function Register) area?

ANSWER

Yes. Define the structure in C and declare an external structure.

For example:

struct s  {
  unsigned int  i;
  unsigned char c;
};

extern struct s MySfr;  // struct should be in SFR space

Then, create an Assembly Module to define the starting address of the external structure.

For example:

PUBLIC MySfr

MySfr DATA  095H       ; start address of struct MySfr

END

MORE INFORMATION

• Refer to Linker Location Controls in the Cx51 User's Guide.

SEE ALSO

• C51: Locating Data Structures in XDATA un the Order Ddefined

Last Reviewed: Thursday, February 25, 2021