C8051F 进不了main函数问题解决办法

这几天在做C8051F340的一个程序，用到USB，我在修改了他的Demo，加了一些数据在xdata里，程序编译通过，无错误无警告，但在仿真的时候一直进不了main函数，我发现很多人遇到了和我一样的问题，在网络上搜索了很长时间，才发现解决之道，现在贴出来共享：

修改STARTUP.A51函数，在启动代码中关闭看门狗如下：

$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 Power-On Initialization of Memory
;
;  With the following EQU statements the initialization of memory
;  at processor reset can be defined:
;
; IDATALEN: IDATA memory size <0x0-0x100>
;     Note: The absolute start-address of IDATA memory is always 0
;            The IDATA space overlaps physically the DATA and BIT areas.
IDATALEN        EQU     80H
;
; XDATASTART: XDATA memory start address <0x0-0xFFFF>
;     The absolute start address of XDATA memory
XDATASTART      EQU     0    
;
; XDATALEN: XDATA memory size <0x0-0xFFFF>
;     The length of XDATA memory in bytes.
XDATALEN        EQU     0     
;
; PDATASTART: PDATA memory start address <0x0-0xFFFF>
;     The absolute start address of PDATA memory
PDATASTART      EQU     0H
;
; PDATALEN: PDATA memory size <0x0-0xFF>
;     The length of PDATA memory in bytes.
PDATALEN        EQU     0H
;
;
;------------------------------------------------------------------------------
;
; Reentrant Stack Initialization
;
;  The following EQU statements define the stack pointer for reentrant
;  functions and initialized it:
;
; Stack Space for reentrant functions in the SMALL model.
;  IBPSTACK: Enable SMALL model reentrant stack
;     Stack space for reentrant functions in the SMALL model.
IBPSTACK        EQU     0       ; set to 1 if small reentrant is used.
;  IBPSTACKTOP: End address of SMALL model stack <0x0-0xFF>
;     Set the top of the stack to the highest location.
IBPSTACKTOP     EQU     0xFF +1     ; default 0FFH+1 
;
;
; Stack Space for reentrant functions in the LARGE model.     
;  XBPSTACK: Enable LARGE model reentrant stack
;     Stack space for reentrant functions in the LARGE model.
XBPSTACK        EQU     0       ; set to 1 if large reentrant is used.
;  XBPSTACKTOP: End address of LARGE model stack <0x0-0xFFFF>
;     Set the top of the stack to the highest location.
XBPSTACKTOP     EQU     0xFFFF +1   ; default 0FFFFH+1
;
;
; Stack Space for reentrant functions in the COMPACT model.   
;  PBPSTACK: Enable COMPACT model reentrant stack
;     Stack space for reentrant functions in the COMPACT model.
PBPSTACK        EQU     0       ; set to 1 if compact reentrant is used.
;
;   PBPSTACKTOP: End address of COMPACT model stack <0x0-0xFFFF>
;     Set the top of the stack to the highest location.
PBPSTACKTOP     EQU     0xFF +1     ; default 0FFH+1 
;
;
;------------------------------------------------------------------------------
;
;  Memory Page for Using the Compact Model with 64 KByte xdata RAM
;  Compact Model Page Definition
;
;  Define the XDATA page used for PDATA variables.
;  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.
;
; PPAGE number <0x0-0xFF>
; uppermost 256-byte address of the page used for PDATA variables.
PPAGE           EQU     0
;
; SFR address which supplies uppermost address byte <0x0-0xFF>
; most 8051 variants use P2 as uppermost address byte
PPAGE_SFR       DATA    0A0H
;
;
;------------------------------------------------------------------------------

; Standard SFR Symbols
ACC     DATA    0E0H
B       DATA    0F0H
SP      DATA    81H
DPL     DATA    82H
DPH     DATA    83H
PCA0MD    DATA  0D9H //Added by auzxj，2009年6月22日

                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
    ANL   PCA0MD, #NOT(040h)//Added by auzxj，2009年6月22日
                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
; Code Banking
; Select Bank 0 for L51_BANK.A51 Mode 4
#if 0  
;     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
;
                LJMP    ?C_START

                END

修改保存，并把它添加进你的工程

====

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修改init.a51文件也可以，里面其实有介绍。
;  User-defined Watch-Dog Refresh.
;
;  If the C application contains many initialized variables uses a watchdog
;  it might be possible that the user has to include a watchdog refresh into
;  the initialization process. The watchdog refresh routine can be included
;  in the following MACRO and can alter all CPU registers except
;  DPTR.
;
WATCHDOG        MACRO
                                ; Include any Watchdog refresh code here
                ENDM
;