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1745D–ATARM–04-Nov-05
AT91M55800A
The following table shows the main steps of an interrupt and the order in which they are per-
formed according to the mode:
Notes: 1. NIRQ de-assertion and automatic interrupt clearing if the source is programmed as level
sensitive
2. Note that software which has been written and debugged using Protect Mode will run cor-
rectly in Normal Mode without modification. However in Normal Mode the AIC_IVR write has
no effect and can be removed to optimize the code.
Action Normal Mode Protect Mode
Calculate active interrupt
(higher than current or spurious)
Read AIC_IVR Read AIC_IVR
Determine and return the vector of the
active interrupt
Read AIC_IVR Read AIC_IVR
Memorize interrupt Read AIC_IVR Read AIC_IVR
Push on internal stack the current priority
level
Read AIC_IVR Write AIC_IVR
Acknowledge the interrupt
(1)
Read AIC_IVR Write AIC_IVR
No effect
(2)
Write AIC_IVR –