Vectored Interrupt Controller (Vic); Features; Description - Philips LPC2194 User Manual

Philips Semiconductors Preliminary User Manual
ARM-based Microcontroller LPC2119/2129/2194/2292/2294

6. VECTORED INTERRUPT CONTROLLER (VIC)

FEATURES

• ARM PrimeCell™ Vectored Interrupt Controller
• 32 interrupt request inputs
• 16 vectored IRQ interrupts
• 16 priority levels dynamically assigned to interrupt requests
• Software interrupt generation

DESCRIPTION

The Vectored Interrupt Controller (VIC) takes 32 interrupt request inputs and programmably assigns them into 3 categories, FIQ,
vectored IRQ, and non-vectored IRQ. The programmable assignment scheme means that priorities of interrupts from the various
peripherals can be dynamically assigned and adjusted.
Fast Interrupt reQuest (FIQ) requests have the highest priority. If more than one request is assigned to FIQ, the VIC ORs the
requests to produce the FIQ signal to the ARM processor. The fastest possible FIQ latency is achieved when only one request
is classified as FIQ, because then the FIQ service routine can simply start dealing with that device. But if more than one request
is assigned to the FIQ class, the FIQ service routine can read a word from the VIC that identifies which FIQ source(s) is (are)
requesting an interrupt.
Vectored IRQs have the middle priority, but ony 16 of the 32 requests can be assigned to this category. Any of the 32 requests
can be assigned to any of the 16 vectored IRQ slots, among which slot 0 has the highest priority and slot 15 has the lowest.
Non-vectored IRQs have the lowest priority.
The VIC ORs the requests from all the vectored and non-vectored IRQs to produce the IRQ signal to the ARM processor. The
IRQ service routine can start by reading a register from the VIC and jumping there. If any of the vectored IRQs are requesting,
the VIC provides the address of the highest-priority requesting IRQs service routine, otherwise it provides the address of a default
routine that is shared by all the non-vectored IRQs. The default routine can read another VIC register to see what IRQs are active.
All registers in the VIC are word registers. Byte and halfword reads and write are not supported.
Additional information on the Vectored Interrupt Controller is available in the ARM PrimeCell™ Vectored Interrupt Controller
(PL190) documentation.
Vectored Interrupt Controller (VIC) 96 May 03, 2004