C51: Problems with #pragma ASM

Information in this article applies to:

• C166 Version 3 and Later
• C251 All Versions
• C51 All Versions

SYMPTOMS

We're having trouble using the pragma directive to introduce assembly code in the middle of a C program. We put '#pragma ASM' to begin assembly code and '#pragma ENDASM' to exit assembly code, but the compiler gave us an error:

'asm/endasm' requires src-control to be active

CAUSE

This error message displays when the SRC directive is not included when using in-line assembly.

RESOLUTION

Specify the SRC directive on the command line whenever you use the #pragma asm/endasm directives.

The SRC directive instructs the C compiler to generate a .SRC file which contains the assembly code generated from your C code. Once you have the .SRC file, you use the assembler to assemble it into an .OBJ file.

If your project does not include any C files that are compiled into OBJ files by the C compiler, you must manually include the proper library files in the project.

If your project does include at least one C file that is compiled into an OBJ file by the C compiler, the linker automatically includes the correct libraries.

MORE INFORMATION

• Refer to SRC in the Cx51 User's Guide.

SEE ALSO

• BL51: Warning L1 (Unresolved External) Using Inline Assembly
• GENERAL: SRC Directive
• C51: Getting Inline Assembly to Work
• C51: Comments in Assembly Blocks
• C51: Inline Assembly Generates Target Out of Range
• C51: in-line assembly gives Compiler Warnings

Last Reviewed: Thursday, February 25, 2021