Lpc2000

Fellows,

In my application it is convenient to switch between IRQ and FIQ in some 
interrupt service routine.
As I know FIQ mode used banked r8-r14 registers and no registers have to be 
saved on stack (providing I want to have the things working :)

So, when an IRQ interrupt occurs, I immediately enter to FIQ, then process my 
interrupt request and then exit..

xxx_IRS:
	msr cpsr_c, #MODE_FIQ|FIQ_BIT|IRQ_BIT	; @ switch to FIQ with ints dsbld.
	... ISR code ...
	msr cpsr_c, #MODE_IRQ|FIQ_BIT|IRQ_BIT	; @ back to IRQ mode
	sub pc,lr,#4						; @ return from interrupt

Everything seems to be working except I am not sure what happens to CPSR of 
the user mode. As I understand, when nIRQ is asserted, CPSR being copied to 
SPSR_irq and on IRQ exit SPSR_irq -> CPSR_usr. But what happens when I switch 
to FIQ and back? Does the CPU core copy cpsr_irq to spsr_fiq and back 
or... ??? In a few words: will be user's CPSR kept alive with such IRQ 
servicing scheme?

Thanks,
Dmitry.