关于如何在C语言中嵌入汇编命令

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C51: GETTING INLINE ASSEMBLY TO WORK

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Information in this article applies to:

• C51 All Versions

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QUESTION

How do I implement inline assembly in C51 using the ASM and ENDASM directives. I have read some of the knowledgebase articles relating to this problem, but I still cannot get it to work.

ANSWER

The following example program, MAIN.C, demonstrates some simple inline assembly.

void main(void){
   test();

#pragma asm
      JMP   $           ; endless loop
#pragma endasm
}

The following rules apply to C51 inline assembly:

• To use #pragma ASM/ENDASM, you must set the Generate Assembler SRC File andAssemble SRC File source file compile options in µVision by right-clicking your source file name in the Project Workspace and selectingOptions for File.
• When using the Generate Assembler SRC File and Assemble SRC File options in µVision, if there are no other C modules in your project, you must manually include the C51 Run-Time Library (C51S.LIB, C51M.LIB, or C51L.LIB).

MORE INFORMATION

• Refer to ASM in the Cx51 User's Guide.
• Refer to Interfacing C to Assembler in the Cx51 User's Guide.

SEE ALSO

• C51: PROBLEMS WITH #PRAGMA ASM
• GENERAL: SRC DIRECTIVE
• BL51: WARNING L1 (UNRESOLVED EXTERNAL) USING INLINE ASSEMBLY
• C51: INLINE ASSEMBLY GENERATES TARGET OUT OF RANGE
• C51: IN-LINE ASM GIVES COMPILER WARNINGS

FORUM THREADS

The following Discussion Forum threads may provide information related to this topic.

• Asembly code in C

Last Reviewed: Thursday, July 17, 2008