C51: MIXING C AND ASSEMBLY

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Information in this article applies to:

• C51 Version 6.02
• µVision Version 2.06

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QUESTION

Do you have any examples of how to mix C and assembly?

ANSWER

The following example program shows how to mix C and assembly in your 8051 programs.

This example starts with a MAIN C function which calls a routine in assembly which then calls a C function.

The MAIN C module appears as follows:

extern void a_func (void);

void main (void)
{
a_func ();
}

The function a_func is an assembly routine:

NAME    A_FUNC

?PR?a_func?A_FUNC    SEGMENT CODE
        EXTRN   CODE (c_func)
        PUBLIC  a_func

        RSEG    ?PR?a_func?A_FUNC
a_func:
        USING   0
        LCALL   c_func
        RET

        END

Note that this assembly routine calls c_func which is a C function:

void c_func (void)
{
}

The actual code for the assembly module was generated using the SRC pragma and the following C source file:

extern void c_func (void);

void a_func (void)
{
c_func ();
}

You may download C2ASM2C.ZIP from the Keil web site.

SEE ALSO

• C51: CALLING ASSEMBLY ROUTINES FROM C
• A51: CALLING C FUNCTIONS FROM ASSEMBLY
• GENERAL: HOW TO CREATE ASSEMBLY FILES FROM C FILES
• C51: ADDING C FUNCTIONS TO EXISTING ASSEMBLER CODE

FORUM THREADS

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

• assembler in c, UART
• Problem in interfacing C files withan assembly file in uVision2 IDE
• Combining C and assembly codes
• Interface a assambler prog. in a C-Prog.

Last Reviewed: Monday, February 05, 2007

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