Dear all: I have some question about what arm will do while exceptions happen. In the document, ARM Architecture Reference Manual located at http://www.arm.com/miscPDFs/14128.pdf, there are some actions will be done when IRQ interrupt happened, A2.6.8.

Below is excerpted from it:

R14_irq = address of next instruction to be executed + 4 SPSR_irq = CPSR CPSR[4:0] = 0b10010 /* Enter IRQ mode */ CPSR[5] = 0 /* Execute in ARM state */ /* CPSR[6] is unchanged */ CPSR[7] = 1 /* Disable normal interrupts */ CPSR[8] = 1 /* Disable Imprecise Data Aborts (v6 only) */ CPSR[9] = CP15_reg1_EEbit /* Endianness on exception entry */ if VE==0 then if high vectors configured then PC = 0xFFFF0018 else PC = 0x00000018 else PC = IMPLEMENTATION DEFINED /* see page A2-26 */

To return after servicing the interrupt, use: SUBS PC,R14,#4

Do these actions have to be done by software or cpu will automatically finish them? Appreciate your help, miloody