首要是中止向量表的设置和现场维护。
调试比较久的原因：运用main: b main时调试发现，不能死循环，可能是main标签是保存的
1）在主程序中的过程一般是：
1.关中止，并设置各首要形式的仓库指针和容量
2写1清SRCPND，INTPND寄存器
3.装备INTMSK使能相应中止
4.开大局中止
3）中止服务程序中的流程是：
1.屏蔽中止(硬件主动关irq中止)
2.执行任务
3.写1清相应SRPND，INTPND等寄存器（能够使用SRPND=SRPND，INTPND来清零，避免犯错）
4.把屏蔽的中止使能回来
5.回来
参阅u-boot的start.S自己写了一个外部中止程序，mini2440的按键K1，按一下LED灭，再按一下LED亮……。硬件原理图：按键引脚对应GPIO是PG0，对应EINT8，而LED的引脚是PB8，被规划为低电平时灯亮。
.equ NOINT, 0xc0 .equ DISABLE_IRQ,0x80.equ SYS_MOD, 0x1f.equ IRQ_MOD, 0x12.equ USR_MOD, 0x10.equ WTCON, 0x53000000.equ GPBCON, 0x56000010.equ GPBDAT, 0x56000014.equ GPBUP, 0x56000018.equ GPGCON, 0x56000060.equ EINTMASK, 0x560000a4 .equ EXTINT1, 0x5600008c .equ EINTPEND, 0x560000a8 .equ INTMSK, 0x4A000008 .equ SRCPND, 0X4A000000 .equ INTPND, 0X4A000010 .equ USE_Stack, 4096.equ IRQ_Stack, 2048.text.code 32.global _start_start: b resetldr 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.balignl 16,0xdeadbeefreset:ldr r0,=WTCONmov r1,#0x0str r1,[r0] @关看门狗ldr r0,=GPBCONldr r1,=0x10000str r1,[r0] @PB8输出ldr r0,=GPBDATmov r1,#0x000str r1,[r0] @低电平msr cpsr_c,#(IRQ_MOD|NOINT)ldr sp,=IRQ_Stackmsr cpsr_c,#(SYS_MOD|NOINT)ldr sp,=USE_Stackldr r0,=GPGCONmov r1,#0x02str r1,[r0] @使能外部中止8ldr r0,=EXTINT1mov r1,#0x03str r1,[r0] @下降沿触发ldr r0, =EINTPEND ldr r1,=0x00fffff0str r1,[r0]@ 清EINTPEND，写1清零ldr r0,=EINTMASKldr r1,=0xfffffeffstr r1,[r0] @使能外部中止8，0为使能ldr r0, =SRCPND ldr r1,=0xffffffffstr r1,[r0]@ 清SRCPND，写1清零ldr r0, =INTPND ldr r1,=0xffffffff str r1,[r0]@ 清INTPND，写1清零ldr r0,=INTMSKldr r1,=0xffffffdfstr r1,[r0] @使能外部中止EINT8-23mrs r1, cpsr bic r1, r1, #DISABLE_IRQmsr cpsr_c, r1 @开大局IRQ中止loop: b loopirq_server:ldr r0, =EINTPENDldr r1,[r0]tst r1,#0x100 @判别是否为EINT8beq not_handle ldr r0,=GPBDATldr r1,[r0]tst r1,#0x100 @测验PB8当时是高电平仍是低电平ldreq r1,=0x100movne r1,#0x0str r1,[r0]not_handle:ldr r0, =EINTPEND ldr r1,[r0] @ldr r1,=0x100str r1,[r0] @清EINTPENDldr r0, =SRCPND ldr r1,[r0] @ldr r1,=0x20str r1,[r0] @清SRCPNDldr r0, =INTPND ldr r1,[r0] @ldr r1,=0x20str r1,[r0] @清INTPNDmov pc,lrundefined_instruction: nop software_interrupt: nop prefetch_abort: nop data_abort: nop not_used: nop irq: sub lr,lr,#4 stmfd sp!,{r0-r12,lr} bl irq_server ldmfd sp!,{r0-r12,pc}^fiq: nop
链接脚本命名为“int.lds”：
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm") OUTPUT_ARCH(arm)ENTRY(_start) SECTIONS{ . = 0x00000000; .text : { *(.text) } .data ALIGN(4): { *(.data) } .bss ALIGN(4): { *(.bss) } }
Makefile是：
led_off.bin : led_off.Sarm-linux-gcc -nostdlib -nostartfiles -g -c -o led_off.o led_off.Sarm-linux-ld -Tint.lds led_off.o -o led_off_elfarm-linux-objcopy -O binary -S led_off_elf led_off.binclean:rm -f led_off.bin led_off_elf *.o
