TL32 ETC, TL32 Datasheet

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Real Time System Testing MIT 16.070 Lecture 32 hperry 5/4/01 ...

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Real Time System Testing (32) • The next three lectures will focus on: – Lecture 30: • How to minimize failure in real time systems • Methods used to test real time systems – Lecture 31: • What is Software ...

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What does it mean for a system to be fault tolerant? The system can operate (although performance may be degraded) in the presence of a software or a hardware failure. How do you design a fault tolerant system? • Incorporate ...

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Some Exception Handling Methods Q: What if your system randomly misses data from a sensor? A: Time tag your system data and use it only if the time tag has been updated since the last time it was used. Sensor ...

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Some Exception Handling Methods Q: What if your system randomly misses data from a sensor? (continued data is too stale and the system cannot function properly without the new data, switch to a degraded mode of operation – ...

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Some Exception Handling Methods Q: What if data goes bad for any number of reasons? What if bad data results in... • Divide by zero in the software algorithm • Data input from sensors out of a specified range (overflow ...

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Some Exception Handling Methods Q: What if a critical task should hang during execution? – For example, a task is waiting on data from a sensor, but the sensor loses its data link to the processor before it can provide ...

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... Adding timeouts on retrieving the data to those functions to drive good/bad status return. Note: • This brings up the need for call by reference in C • This concept can be expanded to operating system calls (posting mailboxes, releasing semaphores), library function calls, etc. provided the RTOS supports it. hperry 5/4/01 ...

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Some Exception Handling Methods The importance of “call by reference” to facilitate error handling • C functions can return only one value • If that value = status, how does the calling task (or function) get any information back from ...

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Some Exception Handling Methods Without exception handling: int y; int get_data(); void light_LED(); while ( get_data(); if (y>100) { light_LED(); } } hperry 5/4/01 /* get data from sensor software*/ /* turn on LEDs */ /* end ...

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Some Exception Handling Methods With exception handling: # include <stdio.h> int y, error; int get_sensor_data(int* x) void light_LED(); while (1) { error = get_sensor_data(&y); if (!error >100) light_LED(); } else printf("Error in data coming from sensor = ...

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... Erroneous mathematical conditions (divide by zero, overflow) – Tasks that hang waiting for inputs that will never come (due to failed hardware, poor communication link, software bug etc.) – Poor reactions to missed deadlines • On the other hand, putting in all of this exception handling takes up resources (CPU time and memory) that must be worth the trade-off • ...

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... CPU testing (done in the background) • Memory testing – Checking for memory corruption due to vibration, power surges, electrostatic discharge, single event upsets, etc. – Use error detection & recovery schemes (CRC, Hamming Code) • Watchdog Timers – Counting registers used to ensure that devices are still on line – ...

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Redundant Hardware Solutions - A two processor scheme Primary • Primary sends replica of all its inputs to Secondary • Secondary runs same software as Primary • Secondary checks for “pulse” from Primary to verify its health • If pulse ...

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Redundant Hardware Solutions - A two processor scheme Primary • When might this scheme fail? – – – hperry 5/4/01 Fault Tolerance Secondary ...

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Fault Tolerance - Redundant Processors • Computers can vote on who is worthy of staying in the system - Check “pulse” sure the computers are on-line - Compare data outputs from computations How many do you need? A ...

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Fault Tolerance - Redundant Processors hperry 5/4/01 A says B is sick B B says A is sick Who is right? Who should take over the system? A says B is sick B B says ...

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Fault Tolerance - Redundant Processors • In some cases 4 computers are necessary, each checking the status of the other hperry 5/4/ there any way that the 4 computer scheme can still fail? D ...

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Fault Tolerance - Redundant Processors Who needs 4 computers and a backup? The Space Shuttle • On ascent and landing/entry the Space Shuttle uses 4 identical computers and one backup. Why? A 1/2 second glitch in the guidance, navigation & ...

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N-Version Programming • Same system requirements for multiple implementations • The different implementations of code are written by independent teams or contractors • Eliminates the common software fault issue • Often used as a backup system hperry 5/4/01 ...

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TEST DOCUMENTATION hperry 5/4/01 ...

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Real Time System Testing (32) Test Documentation (Test Plan / Test Report) • Includes an Executive Summary • Describes test environment • Identifies software to be tested • Identifies tests that will be run on the software • Includes a ...

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Section 1 - Executive Summary • System Overview – Purpose of the system – General operation of the system – History of system development • Document Overview – Summarize contents of the test plan / report – Summarize key test ...

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... Identify what exactly is being tested (i.e. the workstation and handyboard software) • Components in the Software Test Environment – Identifies operating systems, compilers, communications software, related application software, etc. used to test the workstation & handyboard software – Identify version numbers for the various software test environment • Hardware and Firmware – ...

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Section 3 - Test Identification Identify planned tests for the…. • Serial I/O • Thrust Controller • Simulator • Fuel Out Indicator • Altitude and Velocity Display • Integrated System hperry 5/4/01 ...

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Section 4 - Requirements Traceability • Identifies the method used for verification of the requirement: – Analysis – Inspection – Demonstration – Test • Maps each software requirement to a test hperry 5/4/01 ...

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MIT 16.070 Requirements Matrix for Final Project Rqmt # Description 1 The system shall be composed of a controller (implemented on a handyboard), a workstation simulation of the Mars Lander, a graphics package (which shall be supplied to the developer) ...

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Section 4 - Requirements Traceability (continued) Rqmt # Description 12 The simulator will have three types of output. It will: 1. send information to the controller specifying altitude, velocity, and whether there is fuel remaining; 13 The simulator will have ...

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Includes an overall assessment of the software as demonstrated by the test results • Identifies any remaining deficiencies, limitations or constraints that were detected by the tests • Includes recommended improvements in the design, operation or testing of the ...

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... Any general information that aids in the understanding of the test report • May include – a list of abbreviations or acronyms – definitions – background information – test rationale – etc. hperry 5/4/01 Section 6 - Notes ...

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Real Time System Testing - Summary • Over the last 3 lectures, you have learned that test and integration is an important part of developing a real time system. Why? A Real Time System must continue running in the presence ...