Hello,

A return from IRQ or SVC is done with the commands:

SUBS PC, R14_irq, #4

and

MOVS PC, R14_svc

But I am puzzled by the way the processor know to return to usermode. Whats the magic that makes the processor change state ? .. according to the instruction set manual the commands copy the Link register to the PC - that makes the CPU jump, but not change mode ? - the S is supposed to change the 4 ALU bits.

Sincerely Per Hansen

Hi,

I'm also interested in this - did you ever get a resolution?

Thanks,

The current program status register (CPSR) is also restored (from the appropriate SPSR).

Bes regards

Crossware
http://www.crossware.com