Cyclic executives for Bare Hardware

1
Cyclic executives for Bare Hardware

• Chapter 4

2
Topics

• Simple loop cyclic executive
• Frame/slots
• Table-based predetermined schedule cyclic
  executive
• Periodic, aperiodic and interrupt-based task

3
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.

4
Blind Bingo
Display() Read input() Loop update
display() If all done exit() Read
input() End Loop
A c b g k V n m L
s E t y w f D v
z x e
5
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

6
Lets analyze the sample program

• Change task times
• Lets analyze repetition rate of the tasks and how
  it relates to the task table