C51: Locating Variables to Far Const Space

Information in this article applies to:

• C51 Version 7
• CX51 Version 7

QUESTION

I need to write portable code for my programs, and I am using a header file that defines the memory types for the program in a generic way.

For example, to put a constant into ROM I have used the syntax:

_code_ unsigned char MyConst = {0xAC};

With #define _code_ code the resulting syntax is:

code unsigned char MyConst = {0xAC};

Everything works fine this way, but now I want to put the constants into the far const space. However, the definition #define _code_ const far results in syntax errors. What can I do?

Note that I do not want to use the following syntax, since I need to have portable code that works on several platforms:

unsigned char const far MyConst = {0xAC};

ANSWER

The correct syntax is #define _code_ far const which results in:

far const unsigned char MyConst = {0xAC};

This compiles fine with the CX51 Compiler or with the C51 Compiler when you use the OMF2 Directive.

MORE INFORMATION

• Refer to Far Memory in the Cx51 User's Guide.
• Refer to STRING in the Cx51 User's Guide.

SEE ALSO

• C51: Correctly Declaring Variables with Memory Spaces
• C51: Memory Classes for Strings and String Pointers

Last Reviewed: Thursday, February 25, 2021