[U-Boot-Users] question bout exception happen

[loody]

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
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