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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
91 of 571
NXP Semiconductors
UM10316
Chapter 9: LPC29xx Vectored Interrupt Controller (VIC)
•
The IRQ exception has a lower priority than FIQ and is masked out when an FIQ
exception occurs. IRQ service routines should take care of saving and/or restoring the
used registers themselves.
The VIC also provides IRQ and FIQ wake-up events to the Event Router. This enables the
system to wake up upon an interrupt. See also
for interrupt and wake-up
structure.
A representation of the VIC is shown in
. Each interrupt request has its own
configuration:
•
Polarity (active HIGH or LOW): The interrupt request inputs are level-sensitive. The
activation level can be programmed according to the connected peripheral (see
for the recommended setting).
•
Target (IRQ/FIQ): Two targets are possible within the ARM architecture:
–
IRQ, Interrupt request; This target is referred to as TARGET1
–
FIQ, Fast Interrupt request; This target is referred to as TARGET0
•
Priority of the pending interrupt is compared with the priority mask of the selected
target.
–
The interrupt is masked if the priority value of the pending interrupt is equal to or
lower than the value in the priority mask.
–
For each interrupt target, pending interrupt requests with priority above the priority
threshold are combined through a logical OR, and the result is then routed towards
the interrupt target.
Fig 18. Schematic representation of the VIC
Active
High/Low
Priority Mask
FIQ
Priority
Target
IRQ/FIQ
Pending 1
FIQ
IRQ
VECTOR FIQ
VECTOR IRQ
Active
High/Lo w
Enable
Priority
Target
IRQ/FIQ
Pending N
Interrupt Request
N
Interrupt Request 1
INT 1
INT N
Interrupt Selection
Priority Mask
IRQ
Enable