谁动了SP起始地址？

$NOMOD51

;------------------------------------------------------------------------------

;  This file is part of the C51 Compiler package

;  Copyright (c) 1988-2005 Keil Elektronik GmbH and Keil Software, Inc.

;  Version 8.01

;

;  *** <<< Use Configuration Wizard in Context Menu >>> ***

;------------------------------------------------------------------------------

;  STARTUP.A51:  This code is executed after processor reset.

;

;  To translate this file use A51 with the following invocation:

;

;     A51 STARTUP.A51

;

;  To link the modified STARTUP.OBJ file to your application use the following

;  Lx51 invocation:

;

;     Lx51 your object file list, STARTUP.OBJ  controls

;

;------------------------------------------------------------------------------

;

;  User-defined <h> Power-On Initialization of Memory

;

;  With the following EQU statements the initialization of memory

;  at processor reset can be defined:

;

; <o> IDATALEN: IDATA memory size <0x0-0x100>

;     <i> Note: The absolute start-address of IDATA memory is always 0

;     <i>       The IDATA space overlaps physically the DATA and BIT areas.

IDATALEN        EQU     80H

;

; <o> XDATASTART: XDATA memory start address <0x0-0xFFFF> 

;     <i> The absolute start address of XDATA memory

XDATASTART      EQU     0     

;

; <o> XDATALEN: XDATA memory size <0x0-0xFFFF> 

;     <i> The length of XDATA memory in bytes.

XDATALEN        EQU     0      

;

; <o> PDATASTART: PDATA memory start address <0x0-0xFFFF> 

;     <i> The absolute start address of PDATA memory

PDATASTART      EQU     0H

;

; <o> PDATALEN: PDATA memory size <0x0-0xFF> 

;     <i> The length of PDATA memory in bytes.

PDATALEN        EQU     0H

;

;</h>

;------------------------------------------------------------------------------

;

;<h> Reentrant Stack Initialization

;

;  The following EQU statements define the stack pointer for reentrant

;  functions and initialized it:

;

; <h> Stack Space for reentrant functions in the SMALL model.

;  <q> IBPSTACK: Enable SMALL model reentrant stack

;     <i> Stack space for reentrant functions in the SMALL model.

IBPSTACK        EQU     0       ; set to 1 if small reentrant is used.

;  <o> IBPSTACKTOP: End address of SMALL model stack <0x0-0xFF>

;     <i> Set the top of the stack to the highest location.

IBPSTACKTOP     EQU     0xFF +1     ; default 0FFH+1  

; </h>

;

; <h> Stack Space for reentrant functions in the LARGE model.      

;  <q> XBPSTACK: Enable LARGE model reentrant stack

;     <i> Stack space for reentrant functions in the LARGE model.

XBPSTACK        EQU     0       ; set to 1 if large reentrant is used.

;  <o> XBPSTACKTOP: End address of LARGE model stack <0x0-0xFFFF>

;     <i> Set the top of the stack to the highest location.

XBPSTACKTOP     EQU     0xFFFF +1   ; default 0FFFFH+1 

; </h>

;

; <h> Stack Space for reentrant functions in the COMPACT model.    

;  <q> PBPSTACK: Enable COMPACT model reentrant stack

;     <i> Stack space for reentrant functions in the COMPACT model.

PBPSTACK        EQU     0       ; set to 1 if compact reentrant is used.

;

;   <o> PBPSTACKTOP: End address of COMPACT model stack <0x0-0xFFFF>

;     <i> Set the top of the stack to the highest location.

PBPSTACKTOP     EQU     0xFF +1     ; default 0FFH+1  

; </h>

;</h>

;------------------------------------------------------------------------------

;

;  Memory Page for Using the Compact Model with 64 KByte xdata RAM

;  <e>Compact Model Page Definition

;

;  <i>Define the XDATA page used for PDATA variables. 

;  <i>PPAGE must conform with the PPAGE set in the linker invocation.

;

; Enable pdata memory page initalization

PPAGEENABLE     EQU     0       ; set to 1 if pdata object are used.

;

; <o> PPAGE number <0x0-0xFF> 

; <i> uppermost 256-byte address of the page used for PDATA variables.

PPAGE           EQU     0

;

; <o> SFR address which supplies uppermost address byte <0x0-0xFF> 

; <i> most 8051 variants use P2 as uppermost address byte

PPAGE_SFR       DATA    0A0H

;

; </e>

;------------------------------------------------------------------------------



; Standard SFR Symbols 

ACC     DATA    0E0H

B       DATA    0F0H

SP      DATA    81H

DPL     DATA    82H

DPH     DATA    83H



                NAME    ?C_STARTUP





?C_C51STARTUP   SEGMENT   CODE

?STACK          SEGMENT   IDATA



                RSEG    ?STACK

                DS      1



                EXTRN CODE (?C_START)

                PUBLIC  ?C_STARTUP



                CSEG    AT      0

?C_STARTUP:     LJMP    STARTUP1



                RSEG    ?C_C51STARTUP



STARTUP1:



IF IDATALEN <> 0

                MOV     R0,#IDATALEN - 1

                CLR     A

IDATALOOP:      MOV     @R0,A

                DJNZ    R0,IDATALOOP

ENDIF



IF XDATALEN <> 0

                MOV     DPTR,#XDATASTART

                MOV     R7,#LOW (XDATALEN)

  IF (LOW (XDATALEN)) <> 0

                MOV     R6,#(HIGH (XDATALEN)) +1

  ELSE

                MOV     R6,#HIGH (XDATALEN)

  ENDIF

                CLR     A

XDATALOOP:      MOVX    @DPTR,A

                INC     DPTR

                DJNZ    R7,XDATALOOP

                DJNZ    R6,XDATALOOP

ENDIF



IF PPAGEENABLE <> 0

                MOV     PPAGE_SFR,#PPAGE

ENDIF



IF PDATALEN <> 0

                MOV     R0,#LOW (PDATASTART)

                MOV     R7,#LOW (PDATALEN)

                CLR     A

PDATALOOP:      MOVX    @R0,A

                INC     R0

                DJNZ    R7,PDATALOOP

ENDIF



IF IBPSTACK <> 0

EXTRN DATA (?C_IBP)



                MOV     ?C_IBP,#LOW IBPSTACKTOP

ENDIF



IF XBPSTACK <> 0

EXTRN DATA (?C_XBP)



                MOV     ?C_XBP,#HIGH XBPSTACKTOP

                MOV     ?C_XBP+1,#LOW XBPSTACKTOP

ENDIF



IF PBPSTACK <> 0

EXTRN DATA (?C_PBP)

                MOV     ?C_PBP,#LOW PBPSTACKTOP

ENDIF



                MOV     SP,#?STACK-1



; This code is required if you use L51_BANK.A51 with Banking Mode 4

;<h> Code Banking

; <q> Select Bank 0 for L51_BANK.A51 Mode 4

#if 0   

;     <i> Initialize bank mechanism to code bank 0 when using L51_BANK.A51 with Banking Mode 4.

EXTRN CODE (?B_SWITCH0)

                CALL    ?B_SWITCH0      ; init bank mechanism to code bank 0

#endif

;</h>

                LJMP    ?C_START



                END

#include <reg52.h>



int tmp ;



int main(void)

{

        int i = 0;



        return 0;

}