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KEIL C51环境下,汇编与C语言交叉编译的问题

2012-07-20 00:23 405 查看
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

Information in this article applies to:

C51 All Versions

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
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