Real-Time Software Design

Front 1

Real-time systems

Back 1

A software system where
the correct functioning of the system depends on
the results produced by the system and the time
at which these results are produced

Front 2

Soft Vs. Hard real-time system

Back 2

Operation is degraded Vs. operation is incorrect if results are not produced within the time specification.

Front 3

Periodic Stimuli Vs. Aperiodic Stimuli

Back 3

Predictable time intervals Vs. Unpredictable time

Front 4

RT (real time) architectural considerations

Back 4

Real-time systems are therefore usually designed as cooperating processes with a real-time executive controlling these processes.

Front 5

Why is Java not suitable for hard RT?

Back 5

• Not possible to specify thread execution time;
• Different timing in different virtual machines;
• Uncontrollable garbage collection;
• No standard access to system hardware;
• Not possible to do run-time space or timing analysis.

Front 6

JAVA garbage collection

Back 6

Objects that are no longer needed by the program are "garbage" and can be thrown away.

Front 7

RT systems design process steps

Back 7

1) Identify the stimuli
2) Correspondent time constraints
3)Execution platform: Time, power, team of people, cost
4) Combine the stimulus and response processing into concurrent processes.
5) Design algorithms: time, stimuli and response
6) Scheduling system

Front 8

RTOS (Real Time operation System) components

Back 8

Real-time clock: info for process scheduling
Interrupt Handler: Manages aperiodic requests for service
Schedular: Chooses the next process to run
Resource Manager: Allocates memory and processor resources
Dispatcher: Starts process excution

Front 9

Interrupt Servicing

Back 9

Control is transferred automatically to a pre-determined memory location and given the highest priority to execute action.

Front 10

Non pre-emptive Vs. Pre-emptive Scheduling

Back 10

Once starts process runs to completion Vs. process can be stopped for higher priority process.

Front 11

Burglar Alarm System Processes

Back 11