cortex M0 startup代码解析

;/******************************************************************************
; * @file     startup_Nano100Series.s
; * @version  V1.00
; * $Revision: 3 $
; * $Date: 14/01/14 4:17p $ 
; * @brief    CMSIS ARM Cortex-M0 Core Device Startup File
; *
; * @note
; * Copyright (C) 2013 Nuvoton Technology Corp. All rights reserved.
;*****************************************************************************/  
;首先对栈和堆的大小进行定义,并在代码区的起始处建立中断向量表,
;其第一个表项是栈顶地址,第二个表项是复位中断服务入口地址。
;然后在复位中断服务程序中跳转C/C++标准实时库的__main函数。
;复位中断服务入口地址存放于0x0000_0000处。当M0遇到复位信号后,
;则从0x0000000处取出复位中断服务入口地址继而执行复位中断服务程序
;然后跳转__main函数,最后来到C的世界。


; <h> Stack Configuration栈配置,为后期跳转到C语言代码存放参数,地址做准备
; <o> Stack Size (in Bytes) <0x0-0xFFFFFFFF:8>
; </h>
;EQU相当于C语言的define
Stack_Size      EQU     0x00000500;,共1280个字节
;定义一片区域名为STACK,未初始化段,可读可写,8字节对齐
                AREA    STACK, NOINIT, READWRITE, ALIGN=3
;此指令用于分配一片连续的存储区域并初始化为0。表达式为要分配的字节数。
;SPACE可用“%”来代替
Stack_Mem       SPACE   Stack_Size
;__initial_sp表示一个标示,编译器计算这个标示的地址.
__initial_sp


; <h> Heap Configuration
;   <o>  Heap Size (in Bytes) <0x0-0xFFFFFFFF:8>
; </h>


Heap_Size       EQU     0x00000500


                AREA    HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem        SPACE   Heap_Size
__heap_limit


                PRESERVE8
                THUMB


; Vector Table Mapped to Address 0 at Reset
;中断向量表映射到0x00,
                AREA    RESET, DATA, READONLY
                ;使编译器指定一段只读的数据段,段名为reset
                ;EXPORT  __Vectors
                ;EXPORT相当于GLOBLE关键字,声明一个全局变量__vector,
;DCD指令:作用是开辟一段空间,其意义等价于C语言中的地址符“&”
;异常向量表从0x0000_0000开始,初始位置为Stack_Point所在地,
;自动取传入的地址存入SP寄存器中,其他中断存放中断程序地址,
;跳转到ISR中执行程序,具体查看datasheet page 111中描述

__Vectors       DCD     __initial_sp              ; Top of Stack
;取__initianl_sp地址放入0x00000000,
                DCD     Reset_Handler             ; Reset Handler
                DCD     NMI_Handler               ; NMI Handler
                DCD     HardFault_Handler         ; Hard Fault Handler
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     SVC_Handler               ; SVCall Handler
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     PendSV_Handler            ; PendSV Handler
                DCD     SysTick_Handler           ; SysTick Handler


                ; External Interrupts
                DCD     BOD_IRQHandler            ; Brownout low voltage detected interrupt  
                DCD     WDT_IRQHandler            ; Watch Dog Timer interrupt  
                DCD     EINT0_IRQHandler          ; External signal interrupt from PB.14 pin
                DCD     EINT1_IRQHandler          ; External signal interrupt from PB.15 pin
                DCD     GPABC_IRQHandler          ; External interrupt from PA[15:0]/PB[15:0]/PC[15:0]  
                DCD     GPDEF_IRQHandler          ; External interrupt from PD[15:0]/PE[15:0]/PF[7:0]
                DCD     PWM0_IRQHandler           ; PWM 0 interrupt 
                DCD     PWM1_IRQHandler           ; PWM 1 interrupt  
                DCD     TMR0_IRQHandler           ; Timer 0 interrupt
                DCD     TMR1_IRQHandler           ; Timer 1 interrupt  
                DCD     TMR2_IRQHandler           ; Timer 2 interrupt 
                DCD     TMR3_IRQHandler           ; Timer 3 interrupt 
                DCD     UART0_IRQHandler          ; UART0 interrupt
                DCD     UART1_IRQHandler          ; UART1 interrupt
                DCD     SPI0_IRQHandler           ; SPI0 interrupt 
                DCD     SPI1_IRQHandler           ; SPI1 interrupt 
                DCD     SPI2_IRQHandler           ; SPI2 interrupt 
                DCD     HIRC_IRQHandler           ; HIRC interrupt 
                DCD     I2C0_IRQHandler           ; I2C0 interrupt 
                DCD     I2C1_IRQHandler           ; I2C1 interrupt 
                DCD     SC2_IRQHandler            ; SC2 interrupt
                DCD     SC0_IRQHandler            ; SC0 interrupt
                DCD     SC1_IRQHandler            ; SC1 interrupt
                DCD     USBD_IRQHandler           ; USB FS Device interrupt 
                DCD     0                         ; Reserved  
                DCD     LCD_IRQHandler            ; LCD interrupt 
                DCD     PDMA_IRQHandler           ; PDMA interrupt
                DCD     I2S_IRQHandler            ; I2S interrupt 
                DCD     PDWU_IRQHandler           ; Power Down Wake up interrupt
                DCD     ADC_IRQHandler            ; ADC interrupt
                DCD     DAC_IRQHandler            ; DAC interrupt
                DCD     RTC_IRQHandler            ; Real time clock interrupt
                AREA    |.text|, CODE, READONLY


; Reset Handler
;汇编伪指令PROC ENDP 提示编译器子程序开始和结束


Reset_Handler   PROC
;定义全局变量 Reset_Handle   [WEAK]表示弱定义可在其他地方优先
;以便在C中调用Reset_Handle,有利于后期编写复位程序
                EXPORT  Reset_Handler             [WEAK]   
                ;申明main,main在外部定义             
                IMPORT  __main
                ;伪指令,提示编译器main标示在外部定义
                ; 解锁保护寄存器。向RegLockAddr连续写入0x59,0x16,0x88解锁
                LDR     R0, =0x50000100
                LDR     R1, =0x59
                STR     R1, [R0]
                LDR     R1, =0x16
                STR     R1, [R0]
                LDR     R1, =0x88
                STR     R1, [R0]


                ; Init POR具体看手册,
                LDR     R2, =0x50000060
                LDR     R1, =0x00005AA5
                STR     R1, [R2]


                ; Lock register写0,锁住保护寄存器
                MOVS    R1, #0
                STR     R1, [R0]


                LDR     R0, =__main
                ;伪指令,将main地址存入R0中
                BX      R0
                ;跳转到R0所在地址的位置,即__main所在程序,BX跳转且切换指令集
                ENDP


; Dummy Exception Handlers (infinite loops which can be modified)                
;其他中断入口程序,弱定义,进入死循环,以便后期C程序编写中断子程序
NMI_Handler     PROC
                EXPORT  NMI_Handler               [WEAK]
                B       .
                ENDP
HardFault_Handler\;连接符
                PROC
                EXPORT  HardFault_Handler         [WEAK]
                B       .
                ENDP
SVC_Handler     PROC
                EXPORT  SVC_Handler               [WEAK]
                B       .
                ENDP
PendSV_Handler  PROC
                EXPORT  PendSV_Handler            [WEAK]
                B       .
                ENDP
SysTick_Handler PROC
                EXPORT  SysTick_Handler           [WEAK]
                B       .
                ENDP
;缺省中断。不写
Default_Handler PROC


                EXPORT  BOD_IRQHandler            [WEAK]
                EXPORT  WDT_IRQHandler            [WEAK]
                EXPORT  EINT0_IRQHandler          [WEAK]
                EXPORT  EINT1_IRQHandler          [WEAK]
                EXPORT  GPABC_IRQHandler          [WEAK]
                EXPORT  GPDEF_IRQHandler          [WEAK]
                EXPORT  PWM0_IRQHandler           [WEAK]
                EXPORT  PWM1_IRQHandler           [WEAK]
                EXPORT  TMR0_IRQHandler           [WEAK]
                EXPORT  TMR1_IRQHandler           [WEAK]
                EXPORT  TMR2_IRQHandler           [WEAK]
                EXPORT  TMR3_IRQHandler           [WEAK]
                EXPORT  UART0_IRQHandler          [WEAK]
                EXPORT  UART1_IRQHandler          [WEAK]
                EXPORT  SPI0_IRQHandler           [WEAK]
                EXPORT  SPI1_IRQHandler           [WEAK]
                EXPORT  SPI2_IRQHandler           [WEAK]
                EXPORT  HIRC_IRQHandler           [WEAK]
                EXPORT  I2C0_IRQHandler           [WEAK]
                EXPORT  I2C1_IRQHandler           [WEAK]
                EXPORT  SC2_IRQHandler            [WEAK]
                EXPORT  SC0_IRQHandler            [WEAK]
                EXPORT  SC1_IRQHandler            [WEAK]
                EXPORT  USBD_IRQHandler           [WEAK]
                EXPORT  LCD_IRQHandler            [WEAK]
                EXPORT  PDMA_IRQHandler           [WEAK]
                EXPORT  I2S_IRQHandler            [WEAK]
                EXPORT  PDWU_IRQHandler           [WEAK]
                EXPORT  ADC_IRQHandler            [WEAK]
                EXPORT  DAC_IRQHandler            [WEAK]
                EXPORT  RTC_IRQHandler            [WEAK]
                
BOD_IRQHandler
WDT_IRQHandler
EINT0_IRQHandler
EINT1_IRQHandler
GPABC_IRQHandler
GPDEF_IRQHandler
PWM0_IRQHandler
PWM1_IRQHandler
TMR0_IRQHandler
TMR1_IRQHandler
TMR2_IRQHandler
TMR3_IRQHandler
UART0_IRQHandler
UART1_IRQHandler
SPI0_IRQHandler
SPI1_IRQHandler
SPI2_IRQHandler
HIRC_IRQHandler
I2C0_IRQHandler
I2C1_IRQHandler
SC2_IRQHandler
SC0_IRQHandler    
SC1_IRQHandler
USBD_IRQHandler
LCD_IRQHandler
PDMA_IRQHandler
I2S_IRQHandler
PDWU_IRQHandler
ADC_IRQHandler
DAC_IRQHandler
RTC_IRQHandler


                B       .


                ENDP


;缺省对齐方式,具体对齐字节平台相关
                ALIGN


; User Initial Stack & Heap
;宏开关,相当C语言IFDEF,定义__MICROLIB则执行,由于为定义执行ELSE分支
                IF      :DEF:__MICROLIB
                
                EXPORT  __initial_sp
                EXPORT  __heap_base
                EXPORT  __heap_limit
                
                ELSE
                ;外部申明,可用于其他地方初始化栈和堆,调用C之前必须初始化栈
                IMPORT  __use_two_region_memory
                EXPORT  __user_initial_stackheap
__user_initial_stackheap

                LDR     R0, =  Heap_Mem
                LDR     R1, =(Stack_Mem + Stack_Size)
                LDR     R2, = (Heap_Mem +  Heap_Size)
                LDR     R3, = Stack_Mem
                BX      LR


                ALIGN


                ENDIF


                END
 

 

转自:https://blog.csdn.net/CSDN_weng/article/details/50963675

 

 

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