To represent the clock driven scheduling, following assumptions and notations are used. The assumptions are:
- The clock driven scheduling is applicable to deterministic
- . There is a constant number n periodic tasks in the
- A restricted periodic task model can be used such that
- Variations in inter-release times of jobs are negligibly
- The parameters of all periodic tasks are known a
- Each job in Ti is released pi units of time after the previous job in
- Each job Ji,k is ready for execution at its release time ri,k such that
- There are aperiodic jobs released at unexpected time instants.
- Aperiodic jobs are placed in special
- New jobs are added to the queue without need to notify
- When processor is available aperiodic jobs are
- There are no sporadic jobs (this assumption will be relaxed later).
- There are no sporadic jobs.
The notation of clock driven scheduling consists of four different parameters that is used to refer the job. The combination of four parameters is called tuple. The standard notation is Ti = (φi, pi, ei, Di) where Ti refers a periodic task with phase φi, period pi, execution time ei, and relative deadline Di.
- Default phase of Ti is φi = 0, default relative deadline is the period Di =
- Omit elements of the tuple that have default values.
- i) T1 = (1, 10, 3, 6) ⇒ φ1 = 1 , p1 = 10, e1 = 3 , D1 = 6
J1,1 released at 1, deadline 7 and J1,2 released at 11, deadline 17.
- ii) T2 = (10, 3, 6) ⇒ φ2 = 0 , p2 = 10 , e2 = 3 , D2 = 6
J2,1 released at 0, deadline 6 and J2,2 released at 10 and so on…. deadline 16
iii) T3 = (10, 3) ⇒ φ3 = 0, p3 = 10, e3 = 3, D3 = 10.
J3,1 released at 0, deadline 10 and J3,2 released at 10, deadline 20.