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2.5 Programs Required for an Application System
2.5 Programs Required for an Application System
A REALOS/907 application system consists of a program for starting tasks and
initializing the system clock, programs for handling normal processing, programs for
handling abnormal conditions, and programs for extending system processing.
■ Application program structure
Figure 2.5 shows the structure of application programs.
Figure 2.5 Application Program Structure
■ Program for starting Tasks and initializing the system clock
❍ Initialize handler
This is the first handler executed after starting the kernel. Performs the initialization
required for the application system and starts the initial tasks.
■ Programs for handling normal processing
❍ Tasks
Tasks are the basic units of an application program. Application processing is performed
by the operation of multiple tasks.
❍ Interrupt handler
Executed on generation of an interrupt. Interrupt handlers are used to receive processing
requests from peripheral devices and notify these requests to tasks.
❍ Timer handlers
These consist of cyclic handlers which are activated at fixed intervals and alarm handlers
which are activated at a specified time. The handlers are executed as part of the system
clock handler.
These handlers can be treated as interrupt handlers.
■ Programs for handling abnormal conditions
❍ Exception handlers
Exception handlers are programs activated when an abnormal condition occurs during
execution of a task or interrupt handler. An exception handler is executed when a system
call exception or CPU exception is generated.
Task A Task B
Initialize
handler
Interrupt
handler
Timer
handler
Exception
handler
REALOS/907
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