Rev. 3.0, 03/01, page 81 of 390
8.2
Interrupt Sources
8.2.1
On-Chip Module Interrupt
Interrupt sources are derived from on-chip peripheral module Interrupts. Each interrupt provides a
mask bit in each module listed below:
•
PS/2 Keyboard
•
PS/2 Mouse
•
PCMCIA Controller (PCC)
•
Analog Front End (AFE) Interface
•
GPIO
•
Timer
•
Keyboard Controller (KBC)
•
IrDA
•
UART
•
PP
•
SCDI
•
USB
•
ADC
8.2.2
Interrupt Exception Processing and Priority
The priority order of the on-chip modules is determined by software. After detecting the interrupt
request IRQ0# from the Intelligent Peripheral Controller, the CPU must read the NIRR (Interrupt
Request Register) to check the interrupt sources. The interrupt sources will be recorded by the
CPU. The CPU will then determine the priority order and execute the interrupt service based on the
determined priority order. That is to say, the interrupt service will be executed for the interrupt
requests in the order from the highest priority to the lowest.
After the highest priority interrupt service is decided by the CPU, the CPU will set mask bit of
NIMR (Interrupt Mask Register) to those lower priority interrupts and set CPU priority level to the
current serviced one.
One exception is that the CPU can still accept an incoming interrupt, which has higher priority than
the one being serviced. After the CPU completes reading the interrupt request register in each
module, the status of interrupt request for each module is cleared automatically, or by software.
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