accessing local "c" variables in inline assembly

How do I access a local variable in assembly?

Only slightly simplified answer: you don't. Inline assembly in C51 isn't integrated anywhere near well enough with the C compiler to allow such tricks.

Generally, the best idea is to re-evaluate the whole plan: are you absolutely sure that you need inline assembly for the task at hand?

You could either pass the local as a parameter to an assembler routine, or move up and write more of the calling code in assembler.

With C51, you generally mix C and assembler function-by-function, not line-by-line inside a single function.

Try writing a dummy C subroutine passing the variable to it as an argument & returning it unchanged. Check the compiled assembly code & add any instructions to the code between the subroutines entry point & it's return of the value.

Don

thanks,
I have taken the C portion and replaced it with Assembler making the whole module assembler.

re-evaluated why I was doing it seperately.

MT

here is a Sample:

void ProcessSerialSwitch()
{
        data unsigned char i;
        data unsigned char RcvFIFOEmptyFlagLo;
        data unsigned char RcvFIFOEmptyFlagHi;
//      char code Mask[8]={0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80};

/*      MemSwitchReg();
        RcvFIFOEmptyFlagLo=XBYTE[RegAddrReceiveFIFOEmpty];
        RcvFIFOEmptyFlagHi=XBYTE[RegAddrReceiveFIFOEmpty+1];
        MemSwitchRam();
*/
RcvFIFOEmptyFlagLo=0xFF;
RcvFIFOEmptyFlagHi=0xFF;

        //对RcvFIFOEmptyFlagLo，RcvFIFOEmptyFlagHiæ¯ä¸€bit进行检测，若为1，则对åº"串å£æœ‰æ•°æ®
        //ç"±äºŽC语言对ä½æ"作效率低，ä¸"此函数ç»å¸¸è¢«è°ƒç"¨ï¼Œæ"¹ä¸ºæ±‡ç¼–
        //for (i=0;i<SerialCount;i++) {
        //      if (i<8) {if (RcvFIFOEmptyFlagLo&Mask[i]) SerialSwitchReadChar(i);}
        //              else if (RcvFIFOEmptyFlagHi&Mask[i-8]) SerialSwitchReadChar(i);
        //}


        ACC=RcvFIFOEmptyFlagLo;

#pragma asm

        checklo:
                //MOV      A,RcvFIFOEmptyFlagLo
                JZ      checkhi

//              CLR      A
#pragma endasm
                i=0;
#pragma asm

//              MOV      i,A

        testlo:
#pragma endasm
        ACC=RcvFIFOEmptyFlagLo;
#pragma asm
//              MOV      A,RcvFIFOEmptyFlagLo
                JZ       checkhi
        lblrorlo:
                CLR      C
                RRC      A
                JC               doreceivelo
                JZ       checkhi
//              INC              i
#pragma endasm
                i++;
#pragma asm
                JMP              lblrorlo

        doreceivelo:
        //      MOV              RcvFIFOEmptyFlagLo, A
#pragma endasm
        RcvFIFOEmptyFlagLo=ACC;
        SerialSwitchReadChar(i);  //读å–æ•°æ®
        i++;
        ACC=RcvFIFOEmptyFlagLo;
#pragma asm
                //inc      i
                //MOV      A, RcvFIFOEmptyFlagLo
                JNZ      lblrorlo

        checkhi:

#pragma endasm
                i=8;
                ACC=RcvFIFOEmptyFlagHi;
#pragma asm
//              MOV      i,8
//      testhi:
                //MOV      A, RcvFIFOEmptyFlagHi
                JZ       returnintr

        lblrorhi:
                CLR      C
                RRC      A
                JC       doreceivehi
                JZ       returnintr
#pragma endasm
                i++;
#pragma asm
                //INC      i
                JMP      lblrorhi
        doreceivehi:
//              MOV              RcvFIFOEmptyFlagHi, A
#pragma endasm
        RcvFIFOEmptyFlagHi=ACC;
        SerialSwitchReadChar(i);
        i++;
        ACC=RcvFIFOEmptyFlagHi;
#pragma asm
                //inc      i
        //      MOV      A,RcvFIFOEmptyFlagHi
                JNZ      lblrorhi

        returnintr:
                RET


#pragma endasm

}

Forgive my ignorance here, but wouldn't it be ever so much easier to do all that with a little assembly language function?

Forgive my ignorance here

Ignorance of all the OP's carefully-considered reasons that made it not ever so much easier to do all that with a little assembly language function in his particular application...

Surely, he must have had plenty...

;-)

a Sample:

This sample only proves that if you absolutely insist, you can drive a 10-inch nail into concrete using a fine-tip soldering iron, even if you have a perfectly usable hammer at hand.

It spectacularly fails to answer the actual question, though: why the heck would anyone want to do such a thing?

this little snippet

#pragma endasm
                i=8;
                ACC=RcvFIFOEmptyFlagHi;
#pragma asm

access the accumulator in C and, while it MAY not blow it all up, the practice is, at least, dangerous. Thus it does not matter if you can "access local "c" variables in inline assembly" since the whole mess, most likely, will blow up anyhow.

To the OP
rewrite the mess totally in assembler and look up the OVERLAYABLE command to the assembler, that will give you local variables in an assembler routine.

Erik