C166: Locate Variables to Absolute Addresses

Information in this article applies to:

• C166, all versions

QUESTION

My application requires that I locate a struct to an absolute memory address in a battery backup (non-volatile) RAM space.

Is this possible?

ANSWER

The following example locates the struct alarm_control at address 0x128000. This structure is defined in a source file named ALMCTRL.C, and this module contains only the declaration for this structure.

  :
  :
struct alarm_st {
unsigned int alarm_number;
unsigned char enable flag;
unsigned int time_delay;
unsigned char status;
};

#pragma NOINIT // disable zero initialization for alarm_control
struct alarm_st huge alarm_control;
  :
  :

The C166 Compiler generates an object file for ALMCTRL.C and includes a section for variables in the huge memory area. The variable alarm_control is located in the section ?HD?ALMCTRL.

To locate this section, enter under Options for Target - L166 Locate - Users Sections:

?HD?ALMCTRL%HDATA (0x128000)

The L166 SECTIONS directive requires that you enter both the section name and the memory class name.

MORE INFORMATION

• Refer to Sections, Classes, and Groups in the C166 User's Guide.
• Refer to SECTIONS in the L166 User's Guide.

SEE ALSO

• C166: Generating a Call to an Absolute Memory Location
• C166: Locating Program Sections to Special Memory Areas
• C166: Locate Constants To Absolute Addresses

Last Reviewed: Thursday, February 25, 2021