Interrupt System Overview; Interrupt Types - HP 3000 III Series Manual

Interr upt System
8-4.
INTERRUPT TYPES
Interrupts may be divided into three basic types; external inter-
rupts which are signals from the I/O system, and two types of
internal interrupts which typically are unexpected conditions
resulting from program execution. The three interrupt types are
external interrupts (from I/O devices), ICS-type internal inter-
rupts (using the Interrupt Control Stack), and non-ICS internal
interrupts. A comparison of the overall operations of all three
interrupt types is illustrated in figure 8-2. Note that opera-
tions proceed mostly left-to-right. For example, external
interrupts begin by triggering some actions in hadware, then the
interrupt processing environment is set up in software. The
Dispatcher is the part of the operating system which schedules
the execution of processes.
HARDWARE
EXTERNAL
INTERRUPT
ICS·TYPE
INTERNAL
INTERRUP;T
Device
Controller
lOP
CPU
Interrupt
Control
_----...,....;;=::-1
Suck
Interrupt
Receiv.
Code
I/O
P'OI
Interrupt
Control
------~Dn:.;;:ta:l
Stack
DISPATCHER
NON·ICS
INTERNAL
iNTERRUPT
Return to:
Interrupted Process
(Possibly
Dispatcher or
another interrupt)
Start Dispatcher
Figure 8-2. Interrupt System Overview
8-5