Cortex-M3 (NXP LPC1788)之启动代码分析

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Cortex-M3 (NXP LPC1788)之启动代码分析

2019-07-12 12:27发布生成海报

站内文章 / NXP MCU

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在Keil uVision4中新建一个基于NXP1788的工程后，会提示添加启动汇编代码startup_LPC177x_8x.S。该文件进行从汇编到C语言运行环境的初始化工作。

;/*****************************************************************************
; * @file:    startup_LPC177x_8x.s
; * @purpose: CMSIS Cortex-M3 Core Device Startup File
; *           for the NXP LPC177x_8x Device Series 
; * @version: V1.20
; * @date:    07. October 2010
; *------- <<< Use Configuration Wizard in Context Menu >>> ------------------
; *
; * Copyright (C) 2010 ARM Limited. All rights reserved.
; * ARM Limited (ARM) is supplying this software for use with Cortex-M3
; * processor based microcontrollers.  This file can be freely distributed
; * within development tools that are supporting such ARM based processors.
; *
; * THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED
; * OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
; * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
; * ARM SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR
; * CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
; *
; *****************************************************************************/


;  Stack Configuration
;    Stack Size (in Bytes) <0x0-0xFFFFFFFF:8>
; 

Stack_Size      EQU     0x00000200

                AREA    STACK, NOINIT, READWRITE, ALIGN=3
Stack_Mem       SPACE   Stack_Size
__initial_sp


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

Heap_Size       EQU     0x00000400

                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

                AREA    RESET, DATA, READONLY
                EXPORT  __Vectors

__Vectors       DCD     __initial_sp              ; Top of Stack
                DCD     Reset_Handler             ; Reset Handler
                DCD     NMI_Handler               ; NMI Handler
                DCD     HardFault_Handler         ; Hard Fault Handler
                DCD     MemManage_Handler         ; MPU Fault Handler
                DCD     BusFault_Handler          ; Bus Fault Handler
                DCD     UsageFault_Handler        ; Usage Fault Handler
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     SVC_Handler               ; SVCall Handler
                DCD     DebugMon_Handler          ; Debug Monitor Handler
                DCD     0                         ; Reserved
                DCD     PendSV_Handler            ; PendSV Handler
                DCD     SysTick_Handler           ; SysTick Handler

                ; External Interrupts
                DCD     WDT_IRQHandler            ; 16: Watchdog Timer
                DCD     TIMER0_IRQHandler         ; 17: Timer0
                DCD     TIMER1_IRQHandler         ; 18: Timer1
                DCD     TIMER2_IRQHandler         ; 19: Timer2
                DCD     TIMER3_IRQHandler         ; 20: Timer3
                DCD     UART0_IRQHandler          ; 21: UART0
                DCD     UART1_IRQHandler          ; 22: UART1
                DCD     UART2_IRQHandler          ; 23: UART2
                DCD     UART3_IRQHandler          ; 24: UART3
                DCD     PWM1_IRQHandler           ; 25: PWM1
                DCD     I2C0_IRQHandler           ; 26: I2C0
                DCD     I2C1_IRQHandler           ; 27: I2C1
                DCD     I2C2_IRQHandler           ; 28: I2C2
                DCD     SPIFI_IRQHandler          ; 29: SPIFI
                DCD     SSP0_IRQHandler           ; 30: SSP0
                DCD     SSP1_IRQHandler           ; 31: SSP1
                DCD     PLL0_IRQHandler           ; 32: PLL0 Lock (Main PLL)
                DCD     RTC_IRQHandler            ; 33: Real Time Clock
                DCD     EINT0_IRQHandler          ; 34: External Interrupt 0
                DCD     EINT1_IRQHandler          ; 35: External Interrupt 1
                DCD     EINT2_IRQHandler          ; 36: External Interrupt 2
                DCD     EINT3_IRQHandler          ; 37: External Interrupt 3
                DCD     ADC_IRQHandler            ; 38: A/D Converter
                DCD     BOD_IRQHandler            ; 39: Brown-Out Detect
                DCD     USB_IRQHandler            ; 40: USB
                DCD     CAN_IRQHandler            ; 41: CAN
                DCD     DMA_IRQHandler            ; 42: General Purpose DMA
                DCD     I2S_IRQHandler            ; 43: I2S
                DCD     ENET_IRQHandler           ; 44: Ethernet
                DCD     MCI_IRQHandler            ; 45: SD/MMC card I/F
                DCD     MCPWM_IRQHandler          ; 46: Motor Control PWM
                DCD     QEI_IRQHandler            ; 47: Quadrature Encoder Interface
                DCD     PLL1_IRQHandler           ; 48: PLL1 Lock (USB PLL)
				DCD		USBActivity_IRQHandler    ; 49: USB Activity interrupt to wakeup
				DCD		CANActivity_IRQHandler    ; 50: CAN Activity interrupt to wakeup
				DCD		UART4_IRQHandler          ; 51: UART4
				DCD		SSP2_IRQHandler           ; 52: SSP2
				DCD		LCD_IRQHandler            ; 53: LCD
				DCD		GPIO_IRQHandler           ; 54: GPIO
				DCD		PWM0_IRQHandler           ; 55: PWM0
				DCD		EEPROM_IRQHandler         ; 56: EEPROM


                IF      :LNOT::DEF:NO_CRP
                AREA    |.ARM.__at_0x02FC|, CODE, READONLY
CRP_Key         DCD     0xFFFFFFFF
                ENDIF


                AREA    |.text|, CODE, READONLY


; Reset Handler

Reset_Handler   PROC
                EXPORT  Reset_Handler             [WEAK]
				IMPORT  SystemInit
                IMPORT  __main
				LDR     R0, =SystemInit
                BLX     R0
                LDR     R0, =__main
                BX      R0
                ENDP


; Dummy Exception Handlers (infinite loops which can be modified)

NMI_Handler     PROC
                EXPORT  NMI_Handler               [WEAK]
                B       .
                ENDP
HardFault_Handler
                PROC
                EXPORT  HardFault_Handler         [WEAK]
                B       .
                ENDP
MemManage_Handler
                PROC
                EXPORT  MemManage_Handler         [WEAK]
                B       .
                ENDP
BusFault_Handler
                PROC
                EXPORT  BusFault_Handler          [WEAK]
                B       .
                ENDP
UsageFault_Handler
                PROC
                EXPORT  UsageFault_Handler        [WEAK]
                B       .
                ENDP
SVC_Handler     PROC
                EXPORT  SVC_Handler               [WEAK]
                B       .
                ENDP
DebugMon_Handler
                PROC
                EXPORT  DebugMon_Handler          [WEAK]
                B       .
                ENDP
PendSV_Handler  PROC
                EXPORT  PendSV_Handler            [WEAK]
                B       .
                ENDP
SysTick_Handler PROC
                EXPORT  SysTick_Handler           [WEAK]
                B       .
                ENDP

Default_Handler PROC

                EXPORT  WDT_IRQHandler            [WEAK]
                EXPORT  TIMER0_IRQHandler         [WEAK]
                EXPORT  TIMER1_IRQHandler         [WEAK]
                EXPORT  TIMER2_IRQHandler         [WEAK]
                EXPORT  TIMER3_IRQHandler         [WEAK]
                EXPORT  UART0_IRQHandler          [WEAK]
                EXPORT  UART1_IRQHandler          [WEAK]
                EXPORT  UART2_IRQHandler          [WEAK]
                EXPORT  UART3_IRQHandler          [WEAK]
                EXPORT  PWM1_IRQHandler           [WEAK]
                EXPORT  I2C0_IRQHandler           [WEAK]
                EXPORT  I2C1_IRQHandler           [WEAK]
                EXPORT  I2C2_IRQHandler           [WEAK]
                EXPORT  SPIFI_IRQHandler          [WEAK]
                EXPORT  SSP0_IRQHandler           [WEAK]
                EXPORT  SSP1_IRQHandler           [WEAK]
                EXPORT  PLL0_IRQHandler           [WEAK]
                EXPORT  RTC_IRQHandler            [WEAK]
                EXPORT  EINT0_IRQHandler          [WEAK]
                EXPORT  EINT1_IRQHandler          [WEAK]
                EXPORT  EINT2_IRQHandler          [WEAK]
                EXPORT  EINT3_IRQHandler          [WEAK]
                EXPORT  ADC_IRQHandler            [WEAK]
                EXPORT  BOD_IRQHandler            [WEAK]
                EXPORT  USB_IRQHandler            [WEAK]
                EXPORT  CAN_IRQHandler            [WEAK]
                EXPORT  DMA_IRQHandler            [WEAK]
                EXPORT  I2S_IRQHandler            [WEAK]
                EXPORT  ENET_IRQHandler           [WEAK]
                EXPORT  MCI_IRQHandler            [WEAK]
                EXPORT  MCPWM_IRQHandler          [WEAK]
                EXPORT  QEI_IRQHandler            [WEAK]
                EXPORT  PLL1_IRQHandler           [WEAK]
				EXPORT  USBActivity_IRQHandler    [WEAK]
				EXPORT  CANActivity_IRQHandler    [WEAK]
				EXPORT  UART4_IRQHandler          [WEAK]
				EXPORT  SSP2_IRQHandler           [WEAK]
				EXPORT  LCD_IRQHandler            [WEAK]
				EXPORT  GPIO_IRQHandler           [WEAK]
				EXPORT  PWM0_IRQHandler           [WEAK]
				EXPORT  EEPROM_IRQHandler         [WEAK]

WDT_IRQHandler
TIMER0_IRQHandler
TIMER1_IRQHandler
TIMER2_IRQHandler
TIMER3_IRQHandler
UART0_IRQHandler
UART1_IRQHandler
UART2_IRQHandler
UART3_IRQHandler
PWM1_IRQHandler
I2C0_IRQHandler
I2C1_IRQHandler
I2C2_IRQHandler
SPIFI_IRQHandler            
SSP0_IRQHandler
SSP1_IRQHandler
PLL0_IRQHandler
RTC_IRQHandler
EINT0_IRQHandler
EINT1_IRQHandler
EINT2_IRQHandler
EINT3_IRQHandler
ADC_IRQHandler
BOD_IRQHandler
USB_IRQHandler
CAN_IRQHandler
DMA_IRQHandler
I2S_IRQHandler
ENET_IRQHandler
MCI_IRQHandler          
MCPWM_IRQHandler
QEI_IRQHandler
PLL1_IRQHandler
USBActivity_IRQHandler
CANActivity_IRQHandler
UART4_IRQHandler
SSP2_IRQHandler
LCD_IRQHandler
GPIO_IRQHandler
PWM0_IRQHandler
EEPROM_IRQHandler

                B       .

                ENDP


                ALIGN


; User Initial Stack & Heap

                IF      :DEF:__MICROLIB

                EXPORT  __initial_sp
                EXPORT  __heap_base
                EXPORT  __heap_limit

                ELSE

                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

程序完成如下内容的工作：开辟一块大小为Stack_Size的栈空间；标号__initial_sp指向栈顶位置；定义堆空间大小为Heap_Size；建立中断向量表Vectors，cortex-M3规定起始地址必须存放栈顶地址即__initial_sp，紧接着存放复位入口地址，这样内核复位后就会自动从起始地址的下32位取出复位地址执行复位中断服务函数。 Reset_Handler复位中断函数中先EXPORT声明Reset_Handler的全局性，然后分别执行外部的函数SystemInit和__main。

下面对汇编程序中的几个关键字做说明：

AREA伪指令：用于定义代码段和数据段，后跟属性标号。其中“READWRITE”表示可读写，“READONLY”只读属性。根据LPC1788的数据手册描述的存储介质，可知可读写段保持在SRAM区，起始地址为0x1000 0000，代码中的堆栈保存在SRAM空间。只读段保存在Flash区，起始地址为0x0000 0000，代码中的中断向量表保存在Flash空间。因此可以总结出，在0x0000 0000 存放的是栈顶的地址__initial_sp（即0x1000 0200），在0x0000 0004 存放的是Reset_Handler的地址。 LPCaddresS

图1：LPC1788 地址映射 memoryLPC

图2： debug中 0地址的值0x1000 0200 即栈顶地址， 0x0000 0004 地址值为0x0000 00F9（看反汇编可知该值即Reset_Handler的入口如下图）。 0XF9

DCD指令：开辟内存空间，中断向量表建立中使用相当于C语言中的函数指针，每个成员都是函数指针，指向各个中断服务函数。
自此分析了LPC1788的启动，主要包括堆栈初始化，和中断向量表的初始化。LPC1788有内部Flash，所以上点从内部Flash启动，内部Flash的起始地址为0x0000 0000，存放栈顶的地址0x1000 0200。 0x0000 0004存放复位中断的入口地址。LPC1788复位后，从0x0000 0004取出复位入口地址，执行中断复位函数，从而跳转到SystemInit和main C语言函数执行。