Cyclic executives for Bare
Hardware
Chapter 4
1
Topics
Simple loop cyclic executive
 Frame/slots
 Table-based predetermined schedule
cyclic executive
 Periodic, aperiodic and interrupt-based
task

2
The basic systems
Several functions are called in a
prearranged sequence
 Some kind of cooperative scheduling
 You a have a set of tasks and a scheduler
that schedules these tasks
 Types of tasks: base tasks (background),
interrupt tasks, clock tasks
 Frame of slots, slots of cycles, each task
taking a cycle, burn tasks to fill up the left
over cycles in a slot.

3
Blind Bingo
A
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Display();
Read input();
Loop:
update display();
If all done exit();
Read input();
End Loop;
4
Frame/slot/cycle pre-determined
schedule

Example



Your week is frame of 7 slots, each with 24
cycles.
it repeats itself
Lets look at a demo program
5
Lets analyze the sample program
Change task times
 Lets analyze repetition rate of the tasks
and how it relates to the task table

6