在此要注意的是區(qū)別中斷向量表和異常向量表。中斷發(fā)生后總是從IRQ 或者FIQ 異常入口處進入，然后跳轉(zhuǎn)到相應(yīng)的異常處理程序處執(zhí)行，這個異常處理程序一般都是進行查找中斷向量表的操作，然后調(diào)用中斷處理程序。
以下是在應(yīng)用中中斷處理實現(xiàn)的過程：從中不難體會到中斷的處理過程。
定義中斷向量表的物理地址：
代碼
- .equ pISR_DABORT , (_ISR_STARTADDRESS+0x10)
- .equ pISR_RESERVED, (_ISR_STARTADDRESS+0x14)
- .equ pISR_IRQ , (_ISR_STARTADDRESS+0x18)
- .equ pISR_FIQ , (_ISR_STARTADDRESS+0x1c) //異常向量表
- ……………………………………………………………………
- .equ pISR_EINT0 , (_ISR_STARTADDRESS+0x20) //中斷向量表
- .equ pISR_EINT1 , (_ISR_STARTADDRESS+0x24)
- .equ pISR_EINT2 , (_ISR_STARTADDRESS+0x28)
- .equ pISR_EINT3 , (_ISR_STARTADDRESS+0x2c)
代碼
- pISR_EINT0 = (unsigned int)isrEINT0; // isrEINT0 中斷處理程序
- pISR_EINT1 = (unsigned int)isrEINT1;
代碼
- .extern Interrupt_Rbutton
- .global isrEINT0
- isrEINT0:
- IRQHandle Interrupt_Rbutton
代碼
- b HandlerUndef /* handler for Undefined mode */
- b HandlerSWI /* handler for SWI interrupt */
- b HandlerPabort /* handler for PAbort */
- b HandlerDabort /* handler for DAbort */
- .long FileIDTable /* id */
- b HandlerIRQ /* handler for IRQ interrupt */
- b HandlerFIQ
代碼
- HandlerFIQ: HANDLER HandleFIQ
- HandlerIRQ: HANDLER HandleIRQ
- HandlerUndef: HANDLER HandleUndef
- HandlerSWI: HANDLER HandleSWI
- HandlerDabort: HANDLER HandleDabort
- HandlerPabort: HANDLER HandlePabort
代碼
- .macro HANDLER HandleLabel
- sub sp,sp,#4 /* decrement sp(to store jump address) */
- stmfd sp!,{r0} /* PUSH the work register to stack(lr does't push bec
- ause it return to original address) */
- ldr r0,=HandleLabel /* load the address of HandleXXX to r0 */
- ldr r0,[r0] /* load the contents(service routine start address) of
- HandleXXX */
- str r0,[sp,#4] /* store the contents(ISR) of HandleXXX to stack */
- ldmfd sp!,{r0,pc} /* POP the work register and pc(jump to ISR) */
- .endm
代碼
- .macro IRQHandle isrHandle:
- stmdb sp!, {r0-r11, ip, lr} /* save r0-r11, ip, lr */
- ldr r0, =isrHandle
- mov lr, pc
- bx r0 /* jump to user_handle(void) */
- ldmia sp!, {r0-r11, ip, lr} /* restore r0, ip, lr */
- subs pc, r14, #4 /* return from interrupt */
- .endm
運行IsrIRQ代碼：
代碼
- ldr r0,=HandleIRQ @ This routine is needed
- ldr r1,=IsrIRQ @ if there isn't 'subs pc,lr,#4' at 0x18, 0x1c
- str r1,[r0]
代碼
- IsrIRQ:
- sub sp,sp,#4 @ reserved for PC
- stmfd sp!,{r8-r9}
- ldr r9,=INTOFFSET
- ldr r9,[r9]
- ldr r8,=HandleEINT0
- add r8,r8,r9,lsl #2
- ldr r8,[r8]
- str r8,[sp,#8]
- ldmfd sp!,{r8-r9,pc}
在嵌入式系統(tǒng)中異常向量表和中斷向量表都是存于FLASH起始的一段空間中。而異常處理和中斷處理程序都是運行在RAM中的
