Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
747
Interrupt Controller Unit—Intel
®
81341 and 81342
11.5
The Intel
®
81341 and 81342 I/O Processors Interrupt
Controller Unit
The 81341 and 81342 Interrupt Controller Unit (ICU) provides a flexible, low-latency
means for requesting interrupts and minimizing the core’s interrupt handling burden.
All interrupt sources are combined into one of the two internal interrupt exceptions:
IRQ and FIQ.
The interrupt controller provides the following features for managing hardware-
requested interrupts:
• Flexibility to direct interrupt sources to either the FIQ or IRQ internal interrupt
exception
• 17 external interrupt pins.
— One high-priority interrupt pin,
HPI#
.
— Sixteen Maskable Inputs,
XINT[15:0]#
. Note that when the 81341 and 81342
acts as an endpoint with the PCI-X interface, only twelve interrupt inputs
(
XINT[15:4]#
) are available instead of sixteen, as the remaining four become
outputs (
P_INT[D:A]#
).
• Two internal timers sources.
• Peripheral interrupt sources.
• Two Intel XScale
®
processor interrupts.
All interrupts are level sensitive: interrupt sources must keep asserting the interrupt
signal until software causes the source to deassert it.
All interrupt sources are individually maskable with the ICUs Interrupt Control
registers.
Additionally, all interrupts may be quickly disabled by altering the F and I bits in the
CPSR as specified in the ARM Architecture Reference Manual.
When software running on the 81341 and 81342 is vectored to an Interrupt Service
Routine (ISR), it reads the ICUs IRQ Interrupt Vector Register (IINTVEC) or FIQ
Interrupt Vector register (FINTVEC) to quickly retrieve the address for the interrupt
handler of the highest priority active interrupt source.