keil startup.a51 文件

第一部分 keil  启动代码

Startup Code

Startup code is executed immediately upon reset of the target system. The Keil startup code performs (optionally) the following operations in order:

启动代码是单片机复位后最先执行的代码，keil 中的启动代码通常按顺序 完成以下操作

• Clears internal data memory （清空内部数据内存）
• Clears external data memory  （清空外部数据内存）
• Clears paged external data memory  （清空分页的外部数据内存）
• Initializes the small model reentrant stack and pointer （初始化小模型可重入栈和指针）
• Initializes the large model reentrant stack and pointer  
• Initializes the compact model reentrant stack and pointer
• Initializes the 8051 hardware stack pointer   初始化8051硬件栈指针
• Transfers control to code that initializes global variables or to the main C function if there are no initialized global variables  

     将控制权交给全局变量初始代码段，或者如果没有全局代码初始段时交给c语言的main 函数

Following is a list of the startup files that are available. （keil 中可用的启动代码文件）

Startup FileDescriptionSTARTUP.A51Startup code for classic 8051 devices. （这个就是8051系列的启动代码文件了）START_AD.A51Startup code for Analog Devices MicroConverter devices.START390.A51Startup code for Dallas DS80C390/400/41x/5240/5250 contiguous mode devices.START4XX.A51Startup code for Dallas DS89C420/430/440/450 devices.STARTLPC.A51Startup code for NXP LPC700 devices series.START900.A51Startup code for NXP LPC90x - LPC93x devices series.START950.A51Startup code for NXP LPC95x - LPC99x devices series.START_MX.A51Startup code for NXP 80C51MX devices.START751.A51Startup code for NXP 80C75x devices.START_XC.A51Startup code for Infineon XC800 devices.STARTUP32.A51Startup code for ST uPSD32xx devices.STARTUP34.A51Startup code for ST uPSD33xx devices.STARTUP34.A51Startup code for ST uPSD34xx devices.

Copy the appropriate startup file from the \KEIL\C51\LIB\ folder into your project folder and make any changes to the copy.

Each startup file provides assembly constants you may change to control the operations performed at startup.

启动代码文件位于 \KEIL\C51\LIB\  ， 你可以通过修改启动代码文件里的如下常量来匹配自己的程序

Name   DescriptionIDATALEN

Specifies the number of bytes of idata to clear to 0. The default is 80h because most 8051 derivatives contain at least 128 bytes of internal data memory. Use a value of 100h for the 8052 and other derivatives that have 256 bytes of internal data memory

.指明idata存储区被清零的大小， 8051系列芯片至少包含128B 内部数据内存，一般默认值为80h。 8052系列或者其他芯片（内部数据内存为256B）使用100h。

XDATASTART

Specifies the initial xdata address to clear to 0

.

XDATALENIndicates the number of bytes of xdata to clear to 0. The default is 0.PDATASTARTSpecifies the initial pdata address to clear to 0.PDATALENSpecifies the number of bytes of pdata to clear to 0. The default is 0.IBPSTACKSpecifies whether or not the small model reentrant stack pointer (?C_IBP) should be initialized. A value of 1 causes this pointer to be initialized. A value of 0 prevents initialization of this pointer. The default is 0.IBPSTACKTOPSpecifies the top of the small model reentrant stack. The default is 0xFF in idata memory.

The Cx51 Compiler does not check to see if the stack area available satisfies the requirements of the application. It is your responsibility to perform such a test.XBPSTACKSpecifies whether or not the large model reentrant stack pointer (?C_XBP) should be initialized. A value of 1 causes this pointer to be initialized. A value of 0 prevents initialization of this pointer. The default is 0.XBPSTACKTOPSpecifies the top of the large model reentrant stack. The default is 0xFFFF in xdata memory.

The Cx51 Compiler does not check to see if the stack area available satisfies the requirements of the application. It is your responsibility to perform such a test.PBPSTACKSpecifies whether the compact model reentrant stack pointer (?C_PBP) should be initialized. A value of 1 causes this pointer to be initialized. A value of 0 prevents initialization of this pointer. The default is 0.PBPSTACKTOPSpecifies the top of the compact model reentrant stack. The default is 0xFF in pdata memory.

The Cx51 Compiler does not check to see if the stack area available satisfies the requirements of the application. It is your responsibility to perform such a test.PPAGEENABLEEnables (a value of 1) or disables (a value of 0) Port 2 initialization for pdata memory access. The default is 0. pdata addressing uses Port 2 for the upper address (or page) byte.PPAGE

Specifies the value to write to Port 2 of the 8051 for pdata memory access. This value represents the xdata memory page to use for pdata. This is the upper 8 bits of the absolute address range to use for pdata. For example, if the pdata area begins at address 1000h (page 10h) in xdata memory, PPAGEENABLE should be set to 1, andPPAGE should be set to 10h. You must specify the starting pdata address to use to the BL51 Linker using the PDATA directive. For example:

BL51 input modules PDATA (1050H)

Neither the BL51 Linker nor the Cx51 Compiler checks to see if the PDATA directive and thePPAGE startup constant are correctly specified. You must ensure that these parameters contain suitable values.

Copyright © Keil, An ARM Company. All rights reserved.

第二部分 STARTUP.A51 

$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.
;   STARTUP.A51:  这部分代码会在单片机复位后被执行。
;  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