Virtual Plant Tour Stamping – c&p=n#/27;109http:// c&p=n#/27;109 – Vision – E E SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 1

SE-3910 Real-time Systems Week 1, Class 3 [DRAFT] – Virtual Plant Tour – Introductions – Quiz 1 – The first real quiz! – Real-Time System Terminology (cont.) Classifications – Response Time & Latency – Common Approaches & Misconceptions SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling, Some from Dr. Hornick, etc. 2

Real-Time System Terminology Soft – Not destroyed by failure to meet response time Hard – Destroyed by failure to meet a single deadline Firm – Destroyed by failure to meet multiple deadlines SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 3

Discussion On your own: Write which kind of real-time system is being used With your partner, discuss & fill in the explanations SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 4 SystemClassificationExplanation Video Surveillance System for Car Dealership Laser welding robot to construct car frames 2 player air hockey game on game console

Timing Terminology Event – A jump in the program counter Synchronous – Predicatable. Scheduled. In sync with other events Asynchronous – Unpredictable. Unscheduled. External requests Aperiodic – No fixed period, asynchronous Sporadic – Extremely infrequent and aperiodic Punctual – Neither early nor late SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 5

Digibot Circuitry A deterministic system SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 6

Five Misconceptions (paraphrased from Laplante and Ovaske) Real-time Systems are fast All you need is – a real-time OS – a rate-monotonic scheduler – lots of scheduling theory We’ve figured out how to make real-time systems SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 7

Muddiest Point What was the muddiest point in this lecture? (least clear point) Would you like to have an outcomes slide at start/end of lecture notes? How about online? (Which do you prefer more?) SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 8

Response Time & Latency Response time – The time between input events and all possible output events SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 9

Measure your class-mate’s response time SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 10

Instructions Part 1 – One partner should hold the stick while the other partner places their hand around the tape at the end of the stick. Hands should be approximately 1” from the stick. – At some point in the future, the partner drops the stick. Read the numbers off of the stick for response time and record them in the GoogleDoc. – Repeat the experiment 3 times Part 2 – One partner should hold the stick while the other partner places their hands around the tape at the end of the stick. Hands should be approximately shoulder width apart. – At some point in the future, the partner drops the stick. Read the numbers off of the stick for response time and record them in the GoogleDoc. – Repeat the experiment 3 times Partners swap roles… SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 11

Human Systems Sensory: Inputs: Both external & internal Outputs: Nerve signals Nervous: Inputs: Nerve signals Outputs: Intelligent nerve signals Motor: Inputs: Nerve signals Outputs: Precise & powerful motion SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 12

Human Nervous System SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 13

Nerve Speeds Speed of signal transmission along nerve fibers – depends on diameter of fiber & presence of myelin – large fibers have more surface area for signals Speeds – small, unmyelinated fibers = m/sec – small, myelinated fibers = m/sec – large, myelinated fibers = up to 120 m/sec Functions – slow signals supply the stomach & dilate pupil – fast signals supply skeletal muscles & transport sensory signals for vision & balance SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 14

System Diagram SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 15 Delays Distance from stick to eyes Speed of light Neuron distance between eyes and brain stem.1 metre Neuron distance between brain and hands 1 metre Time for hands to close Hands can move up to 100 mph (44 metres per second) Rest of time will be latency in the brain m / s (google)

Latency vs. Processing Time? time-vs-latency/ time-vs-latency/ Latency + Processing Time = Response Time (One view) What response time can we guarantee with our system? – What is epsilon? SE Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 16