2440核心初始化

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异常向量表

异常：
因为内部或者外部的一些事件，导致处理器停下正在处理的工作，转而去处理这些发生的时间。
Resset 重启异常
Undefined instructions 未定义异常
Software interrupt 软件中断异常
Prefeth Abort 预取指令异常
dATA aBORT 赌气数据失败残生的Data Abort异常
IRQ 中断异常
FIQ 快速中断异常
异常向量：
当一种异常发生的时候，ARM处理器会跳转到对应异常的固定地址去执行异常处理程序，而这个固定的地址，就称之为异常向量。
异常向量表：
由7个异常及其处理函数跳转关系组成的表即为异常向量表
0x00000000: b reset
0x00000004: ldr pc, _undefined_instruction
0x00000008: ldr pc, _software_interrupt
0x0000000c: ldr pc, _prefetch_abort
0x00000010: ldr pc, _data_abort
0x00000014: ldr pc, _not_used
0x00000018: ldr pc, _irq
0x0000001c: ldr pc, _fiq
范例代码：

.text.global _start_start:        b   reset                               ldr pc, _undefined_instruction          ldr pc, _software_interrupt             ldr pc, _prefetch_abort                 ldr pc, _data_abort                     ldr pc, _not_used                       ldr pc, _irq                            ldr pc, _fiq_undefined_instruction: .word undefined_instruction_software_interrupt:    .word software_interrupt_prefetch_abort:    .word prefetch_abort_data_abort:        .word data_abort_not_used:      .word not_used_irq:           .word irq_fiq:           .word fiq                   undefined_instruction:        nopsoftware_interrupt:        nopprefetch_abort:        nopdata_abort:        nopnot_used:        nopirq:        nopfiq:        nopreset:        nop

设置svc模式

范例代码：

.text.global _start_start:        b   reset                               ldr pc, _undefined_instruction          ldr pc, _software_interrupt             ldr pc, _prefetch_abort                 ldr pc, _data_abort                     ldr pc, _not_used                       ldr pc, _irq                            ldr pc, _fiq_undefined_instruction: .word undefined_instruction_software_interrupt:    .word software_interrupt_prefetch_abort:    .word prefetch_abort_data_abort:        .word data_abort_not_used:      .word not_used_irq:           .word irq_fiq:           .word fiq                   undefined_instruction:        nopsoftware_interrupt:        nopprefetch_abort:        nopdata_abort:        nopnot_used:        nopirq:        nopfiq:        nopreset:        bl set_svcset_svc:        mrs r0, cpsr        bic r0, r0, #0x1f        orr r0, r0, #0xd3        msr cpsr, r0        mov pc, lr

关闭看门狗

.text.global _start_start:        b   reset                               ldr pc, _undefined_instruction          ldr pc, _software_interrupt             ldr pc, _prefetch_abort                 ldr pc, _data_abort                     ldr pc, _not_used                       ldr pc, _irq                            ldr pc, _fiq_undefined_instruction: .word undefined_instruction_software_interrupt:    .word software_interrupt_prefetch_abort:    .word prefetch_abort_data_abort:        .word data_abort_not_used:      .word not_used_irq:           .word irq_fiq:           .word fiq                   undefined_instruction:        nopsoftware_interrupt:        nopprefetch_abort:        nopdata_abort:        nopnot_used:        nopirq:        nopfiq:        nopreset:        bl set_svc        bl disable_watchdogset_svc:        mrs r0, cpsr        bic r0, r0, #0x1f        orr r0, r0, #0xd3        msr cpsr, r0        mov pc, lr#define pWTCON 0x53000000disable_watchdog:        ldr r0, =pWTCON        mov r1, #0x0        str r1, [r0]        mov pc, lr

关闭中断

.text.global _start_start:    b reset    ldr pc, _undifined_instruction    ldr pc, _software_interrupt    ldr pc, _prefetch_abort    ldr pc, _data_abort    ldr pc, _not_used    ldr pc, _irq    ldr pc, _fiq_undifined_instruction: .word undifined_instruction_software_interrupt: .word software_interrupt_prefetch_abort: .word prefetch_abort_data_abort: .word data_abort_not_used: .word not_used_irq: .word irq_fiq: .word resetundifined_instruction:    nopsoftware_interrupt:    nopprefetch_abort:    nopdata_abort:    nopnot_used:    nopirq:    nopfiq:        nopreset:    bl set_svc    bl disable_watchdog    bl disable_interruptset_svc:    mrs r0, cpsr    bic r0, r0,#0x1f    orr r0, r0,#0xd3    msr cpsr, r0    mov pc, lr#define pWTCON 0x53000000disable_watchdog:    ldr r0, =pWTCON    mov r1, #0x0    str r1, [r0]    mov pc, lrdisable_interrupt:    mvn r1, #0x0    ldr r0, =0x4a000008    str r1, [r0]    mov pc, lr

关闭MMU

.text.global _start_start:    b reset    ldr pc, _undifined_instruction    ldr pc, _software_interrupt    ldr pc, _prefetch_abort    ldr pc, _data_abort    ldr pc, _not_used    ldr pc, _irq    ldr pc, _fiq_undifined_instruction: .word undifined_instruction_software_interrupt: .word software_interrupt_prefetch_abort: .word prefetch_abort_data_abort: .word data_abort_not_used: .word not_used_irq: .word irq_fiq: .word resetundifined_instruction:    nopsoftware_interrupt:    nopprefetch_abort:    nopdata_abort:    nopnot_used:    nopirq:    nopfiq:        nopreset:    bl set_svc    bl disable_watchdog    bl disable_interrupt    bl disable_mmuset_svc:    mrs r0, cpsr    bic r0, r0,#0x1f    orr r0, r0,#0xd3    msr cpsr, r0    mov pc, lr#define pWTCON 0x53000000disable_watchdog:    ldr r0, =pWTCON    mov r1, #0x0    str r1, [r0]    mov pc, lrdisable_interrupt:    mvn r1, #0x0    ldr r0, =0x4a000008    str r1, [r0]    mov pc, lrdisable_mmu:    mcr p15,0,r0,c7,c7,0    mrc p15,0,r0,c1,c0,0    bic r0, r0, #0x00000007    mcr p15,0,r0,c1,c0,0    mov pc, lr

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