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online asm in c51, what is the matter?

11 22

I use this code:

#include <reg52.h>

void main(void)
{
  unsigned char data x8,x9,x10;
  while(1)
  {
  x8 = 0;
  x9 = 9;
  x10 = x8 + x9;
  __asm CLR A;
  }
}

and the SRC file is look like this, I think this is right:
; void main(void)

	RSEG  ?PR?main?MAIN
main:
	USING	0
			; SOURCE LINE # 5
; {
			; SOURCE LINE # 6
?C0001:
;   unsigned char data x8,x9,x10;
;   while(1)
			; SOURCE LINE # 8
;   {
			; SOURCE LINE # 9
;   x8 = 0;
			; SOURCE LINE # 10
;---- Variable 'x8?040' assigned to Register 'R7' ----
	CLR  	A
	MOV  	R7,A
;   x9 = 9;
			; SOURCE LINE # 11
;---- Variable 'x9?041' assigned to Register 'R6' ----
	MOV  	R6,#09H
;   x10 = x8 + x9;
			; SOURCE LINE # 12
	ADD  	A,R6
	MOV  	x10?042,A
;   __asm CLR A;
	 CLR A;
;   }
			; SOURCE LINE # 14
	SJMP 	?C0001
	RET  	
; END OF main

	END

But, when Debug it, it look like this in debug window:
C_STARTUP:
C:0x0000    020003   LJMP     STARTUP1(C:0003)
STARTUP1:
C:0x0003    787F     MOV      R0,#0x7F
C:0x0005    E4       CLR      A
IDATALOOP:
C:0x0006    F6       MOV      @R0,A
C:0x0007    D8FD     DJNZ     R0,IDATALOOP(C:0006)
C:0x0009    758108   MOV      SP(0x81),#0x08
C:0x000C    020000   LJMP     C_STARTUP(C:0000)========>You see here!!!
MAIN:
C:0x000F    E4       CLR      A
C:0x0010    FF       MOV      R7,A
C:0x0011    7E09     MOV      R6,#0x09
C:0x0013    2E       ADD      A,R6
C:0x0014    F508     MOV      0x08,A
C:0x0016    E4       CLR      A
C:0x0017    80F6     SJMP     MAIN(C:000F)
C:0x0019    22       RET

do you know why?

Parents
  • 0

    The code is right, what do you think is wrong?

    If you don't use optimizing, you will see that x8 was assigned an address of 8 and x9 of 9, and x10 of 10. But if you use high level optimizing, the compiler will use some registers assign to the local variables, as in the target file, the x8 was r7, and x9 is r6, but x10 was kept as a non-register varable still and its address was 8.

    The first 'CLR A' was used to generate a zero for the operation 'X8=0', and the second one was generated by your __asm.



Reply
  • 0

    The code is right, what do you think is wrong?

    If you don't use optimizing, you will see that x8 was assigned an address of 8 and x9 of 9, and x10 of 10. But if you use high level optimizing, the compiler will use some registers assign to the local variables, as in the target file, the x8 was r7, and x9 is r6, but x10 was kept as a non-register varable still and its address was 8.

    The first 'CLR A' was used to generate a zero for the operation 'X8=0', and the second one was generated by your __asm.



Children
  • 0 in reply to John X. Liu

    I means that the debug is wrong.

    You can see the common I add there, it should not be that:
    But, when Debug it, it like like this in debug window:

    C_STARTUP:
C:0x0000    020003   LJMP     STARTUP1(C:0003)
STARTUP1:
C:0x0003    787F     MOV      R0,#0x7F
C:0x0005    E4       CLR      A
IDATALOOP:
C:0x0006    F6       MOV      @R0,A
C:0x0007    D8FD     DJNZ     R0,IDATALOOP(C:0006)
C:0x0009    758108   MOV      SP(0x81),#0x08
C:0x000C    020000   LJMP     C_STARTUP(C:0000)========>You see here!!!
MAIN:
C:0x000F    E4       CLR      A
C:0x0010    FF       MOV      R7,A
C:0x0011    7E09     MOV      R6,#0x09
C:0x0013    2E       ADD      A,R6
C:0x0014    F508     MOV      0x08,A
C:0x0016    E4       CLR      A
C:0x0017    80F6     SJMP     MAIN(C:000F)
C:0x0019    22       RET

  • 0 in reply to 11 22

    In my debug windows, it shows:

    C:0x0009 75 81 08 MOV SP(0x81), #0x08
C:0x000C 02 00 0F LJMP MAIN(C:000F)
C:0x000F E4 CLR A <==== MAIN

    What optimization level and c51 options did you use? How did you compile the file?

  • 0 in reply to 11 22

    What linker errors did you receive?

    Jon

  • 0 in reply to John X. Liu

    All options are deault.
    BTW, my uv2 is the newest one, 6.21

  • 0 in reply to Jon Ward

    No errors, just warrings:

    Build target 'Target 1'
compiling main.c...
assembling main.src...
linking...
*** WARNING L1: UNRESOLVED EXTERNAL SYMBOL
SYMBOL:  ?C_STARTUP
MODULE:  main.obj (MAIN)
creating hex file from "c_asm"...
"c_asm" - 0 Error(s), 1 Warning(s).

  • 0 in reply to Jon Ward

    Ahhhh. This warning indicates what the problem is. It is usually NOT SAFE to ignore linker errors or warnings.

    The problem is that you have no C modules in your program. Since you use the SRC directive to get an assembler module (from a C module) the program is really an assembler program.

    In such a case, you must manually include the correct C library to get the startup and initialization code routines. Refer to the following knowledgebase article for details on how to do that.

    http://www.keil.com/support/docs/1646.htm

    Larger programs with a few inline assembler modules will not exhibit this problem since there is likely to be at least one C module.

    Jon

  • 0 in reply to Jon Ward

    Thanks a lot.

    I add c51s.lib into my test project, and it seems everything is OK.