KEIL C51环境下，汇编与C语言交叉编译的问题

1. 关于如何在C语言中嵌入汇编命令：

转载自：http://www.keil.com/support/docs/2308.htm

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

 

2.  关于如何将C语言源文件转化为汇编文件：

--转载自：http://blog.21ic.com/user1/6088/archives/2010/68469.html

方法：（假设当前工程中只有一个C代码文件）

       第1步：新建一个工程，添加C文件，编译通过

       第2步：右击Keil界面中Project Workspace里的C文件名，选择‘Option for…’

       第3步：点击‘Generate Assembler SRC File’‘Assemble SRC File’两个三态复选框使它们呈高亮并勾选，点击确定

       第4步：将KEIL安装目录下C51/LIB/C51S.LIB（如果是SMALL模式）文件复制到工程目录下

       第5步：添加库文件C51S.LIB文件到工程，即右击‘Source Group 1’，选择‘Add Files to Group …’，在工程目录下选择C51S.LIB，点击打开

       （因为有了第3步中的操作，如果在这里不添加库文件，则编译生成的HEX文件不能被单片机正确执行，同时编译时会出现一个警告：

WARNING L1:UNRESOLVED EXTERNAL SYMBOL

SYMBOL:  ?C_STARTUP

无法识别?C_STARTUP这个标号，这个标号是在库文件中定义

）

       第6步：打开工程目录，可以看到新生成一个扩展名为.SRC的文件，将其扩展名改成.A51

       第7步：添加这个.A51文件到工程（这时候工程就包含C51S.LIB库文件，不然编译会产生第5步中说明的警告，且生成的HEX文件不能被单片机正确运行）

       第8步：重新编译，生成HEX文件，加载到单片机中，可以发现与C语言运行的现象是一致的