1. Designing Realtime Systems & Embedded Systems B. Ramamurthy CSE 321 12/13/20151

2. The course will enable you to: Understand and design embedded systems and real-time systems For real-time systems: ◦ Identify the unique characteristics of real-time systems ◦ Explain the general structure of a real-time system ◦ Define the design problems and challenges of real-time systems ◦ Apply real-time systems design techniques to various software programs. 12/13/20152

3. Course overview For embedded systems it will enable you to : ◦ Understand the basics of an embedded system ◦ Program an embedded system ◦ Design, implement and test an embedded system. ◦ Ex: realtime + embedded : heart pacemaker ◦ Ex: realtime: online video games 12/13/20153

4. Global Embedded Systems Market Global Embedded Systems Market, 2003-2009($ Millions): Source BBC Inc. http://www.the-infoshop.com/study/bc31319-embedded-systems.html 12/13/20154

5. Example real-time and embedded systems DomainApplication AvionicsNavigation; displays MultimediaGames; simulators MedicineRobot surgery; remote surgery; medical imaging Industrial systemsRobot assembly lines; automated inspection CivilianElevator control Automotive system; Global positioning system (GPS) 12/13/20155

6. Lets discuss some realtime system (RTS) characteristics 12/13/20156

7. Realtime Characteristics RTS have to respond to events in a certain pre-detemined amount of time. ◦ The time constraints have to be considered during planning, design, implementation and testing phases. Internal failures due to software and hardware fault have be handled satisfactorily. ◦ You cannot simply pop-up a dialog error box that says “send report” or “don’t send report”. ◦ Also external failures due to outside sources need to be handled. 12/13/20157

8. Realtime Characteristics (contd.) Typical interaction in an RTS is asynchronous. Thus an RTS should have features to handle asynchronous events such as interrupt handlers and dispatcher and associated resources. Potential for race condition: when state of resources are timing dependent race condition may occur. Periodic tasks are common. 12/13/20158

9. Embedded System Is a special purpose system designed to perform a few dedicated functions. Small foot prints (in memory) Highly optimized code Cell phones, mp3 players are examples. The components in an mp3 player are highly optimized for storage operations. (For example, no need to have a floating point operation on an mp3 player!) 12/13/20159

10. Real-time system concepts A system is a mapping of a set of input into a set of outputs. A digital camera is an example of a realtime system: set of input including sensors and imaging devices producing control signals and display information. Realtime system can be viewed as a sequence of job to be scheduled. Time between presentation of a set of inputs to a system and the realization of the required behavior, including availability of all associated outputs, is called the response time of the system. 12/13/201510

11. Real-time system concepts (contd.) Real-time system is the one in which logical correctness is based on both the correctness of the output as well as their timeliness. A soft real-time system is one in which performance is degraded by failure to meet response-time constraints. A hard real-time system is one in which failure to meet a single deadline may lead to complete and catastrophic failure. More examples: ◦ Automatic teller: soft ◦ Robot vacuum cleaner: firm ◦ Missile delivery system: hard ◦ Given a system you should be able to classify it. 12/13/201511

12. Embedded Systems 12/13/201512

13. Requirements-Engineering Process Deals with determining the goals, functions, and constraints of systems, and with representation of these aspects in forms amenable to modeling and analysis. 12/13/201513

14. Types of requirements Standard scheme for realtime systems is defined by IEEE standard IEEE830. It defines the following kind of requirements: I.Functional II.Non-functional 1.External interfaces 2.Performance 3.Logical database 4.Design constraints (ex: standards compliance) 5.Software system attributes Reliability, availability, security, maintainability, portability 12/13/201514

15. Design methods: Finite state machines Finite state automaton (FSA), finite state machine (FSM) or state transition diagram (STD) is a formal method used in the specification and design of wide range of embedded and realtime systems. The system in this case would be represented by a finite number of states. Lets design the avionics for a drone aircraft. 12/13/201515

16. Drone aircraft avionics (simplified) TAK LAN NAA NAE NAV else MA else TD else LO else EE ED MC MA: Mission Assigned TD: Target Detected LO: Locked On EE: enemy Evaded ED: Enemy Destroyed MC: Mission Complete TAK: Take off NAV: Navigate NAE: Navigate & Evade NAA: Navigate & Attack LAN: Land 12/13/201516

17. Finite State Machine (FSM) M = five tuple  { S, i, T, Σ, δ } S = set of states i = initial state T = terminal state (s) Σ = events that bring about transitions δ = transitions Lets do this exercise for the avionics for fighter aircraft 12/13/201517

18. State Transition table MALOTDMCEEED TAKNAV NAELAN NAENAA NAENAV LAN 12/13/201518

19. Lets design a simple embedded/ realtime system Use the table-cell to code a function / use with switch statement Or write a table-driven code Which is better and why? 12/13/201519

20. Summary We examined the course objectives for embedded and realtime systems We looked at sample systems FSM are common approach to design RTS/EMB Brush up your programming language skills 12/13/201520