Interrupt Pending Function Types - Samsung S3F84B8 User Manual

S3F84B8_UM_REV 1.00 5 INTERRUPT STRUCTURE

5.1.13 INTERRUPT PENDING FUNCTION TYPES

5.1.13.1 Overview of Interrupt Pending Function Types
There are two types of interrupt pending bits: one that is automatically cleared by the hardware after the interrupt
service routine is acknowledged and executed and the other that must be cleared in the interrupt service routine.
5.1.13.2 Pending Bits Cleared Automatically by the Hardware
For interrupt pending bits that are cleared automatically by the hardware, interrupt logic sets the corresponding
pending bit to "1" when a request occurs. It then issues an IRQ pulse to inform the CPU that an interrupt is waiting
to be serviced. The CPU acknowledges the interrupt source by sending an IACK, executes the service routine,
and clears the pending bit to "0". This type of pending bit is not mapped and cannot be read or written by the
application software.
In S3F84B8 interrupt structure, TimerA, TimerD, and PWM counter overflow interrupts belong to this category of
interrupts, where pending bits can be cleared automatically by the hardware.
5.1.13.3 Pending Bits Cleared by the Service Routine
The second type of pending bit is the one that should be cleared by the program software. The service routine
must clear appropriate pending bit before a return-from-interrupt subroutine (IRET) occurs. To do this, a "0" must
be written to the corresponding pending bit location in the source's mode or control register.
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