这是以前我遇到的，在ednchina上发过，现重新整理了一下，我的目标是ARM9，谁都表跟我抢
提出问题：
前一阵在做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
分析问题：
子曾经曰过：“知之为知之，不知google之，是知也”。于是遇到这问题，我首先google之，发现很多人遇到了和我一样的问题，还有很多人在百度知道上提出了，但一直没有解决，经过查阅大量的网页，借鉴别人的经验，站在前辈的肩上（没跟他们商量，我就自作主张站上去了 ），再加上自己的一点点思考，终于发现问题的存在
单片在进入main函数之前，会执行启动代码，由于我长时间用C，潜意识CPU上电就会跳到main的入口，我记得N年以前写汇编的时候，也是在0000H地址处加一个跳转指令直接跳到main函数的，从来没注意过启动代码，这次栽了跟头才好好的看了看
由于我原程序在xdata开辟了大量的数据，在启动代码中
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
会执行xdata的初始化，由于C8051F340有看门狗，而看门狗默认是开启的，我一般会在main函数的第一句话把看门狗关闭，由于定义的xdata很大，在启动代码中执行初始化时间远远超过了喂狗时间，所有导致执行启动代码的过程中看门狗复位，一直进不了主程序，关不了狗，够就一直复位，无限循环。。。。。
解决问题：
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 <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> PAGE 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
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
;<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
//修改保存，并把它添加进你的工程 |
，这次可是当着业界有力人士的面。好彩此兄似乎未注意到
STM32
MCU
通讯及无线技术
物联网技术
电子DIY
板卡试用
基础知识
软件与操作系统
我爱生活
小e食堂