Hi all,
I’m a bit confused about the handling of the FSR0 and FSR2 pointer during the ISR’s - is it saved when entering and restored on exiting the ISR, or carried into the ISR and lost on exit or…?
From the words of the Boss:
Following registers are dedicated for mainprograms, they will not be automatically saved before an interrupt call:
TMP1…TMP5 and FSR0
Following registers are dedicated for interrupt service routines, they shouldn’t be used by mainprograms:
IRQ_TMP1…IRQ_TMP5 and FSR2
Following registers are stored automatically by the interrupt handler before a hook will be called, and they will be restored before the interrupt will be finished - therefore they can be used by the mainprogram and by ISRs without conflicts:
FSR1, TBLPTRL, TBLPTRH, TABLAT, MIOS_PARAMETER1…MIOS_PARAMETER3
And then on the ram handling doc available on the download page at ucapps.de:
Question from Duggle:
> Does FSR2 get saved and restored in the ISRs?
> (if not then it can’t be used in user routines without disabling interrupts)?
> MIOS routines use FSR1 so if I use FSR1 completely in-between MIOS calls it
> should be ok? (MIOS may destroy FSR1’s content)
> Are there any dangers of using FSR0? (It gets used by main, are there
> any user hooks that should restore its content for use by main?
Answer:
All FSRs (FSR0, FSR1 and FSR2) as well as TBLPTR[LH], TABLAT and
MIOS_PARAMETER[123] are stored by the interrupt handler.
Yes, you can use FSR1 in between MIOS calles in your main program and in
interrupt service routines w/o problems.
What does happen to FSR0 and FSR2? Am I missing something?
