Typically, this is often accomplished by converting the sequential design into a scan design with 3 modes of operation they are, normal mode. Design for testing or design for testability dft consists of ic design techniques that add testability features to a hardware product design. With the growth in complexity of very large scale integration vlsi. At the same time, growing competition and high user expectations for quality pcbs demand greater performance and fewer defects. Dft techniques improve quality while reducing cost of test. Neglecting testability during software development increases technical debt and has severe consequences on systems that are destined to operate for many years. Comments 5 to design for testability stephan schwab wrote thank you george for writing this post. The list of acronyms and abbreviations related to dft design for testability. In this article, ill discuss where testability and design are aligned with one another and where they are not. In the interrim, michael feathers wrote a blog entry entitled the deep synergy between testability and good design.
Lecture 14 design for testability testing basics stanford university. This voluminous book has a lot of details and caters to newbies and professionals. Design for testability 14cmos vlsi designcmos vlsi design 4th ed. Design for testability techniques zebo peng, ida, lithzebo peng, ida, lith tdts01 14 tdts01 lecture notes lecture 9lecture notes lecture 9 design for testability dft to take into account the testing aspects during the design process so that more testable designs will be generated. Designfortestability needs to be considered during layout to prevent signal integrity problems and ensure a working scan chain. Design for test aka design for testability or dft is a name for design techniques that add certain testability features to a microelectronic hardware product design. Ive been saying the same many times but here and there people seem to be opposed to the idea because it may change architecture so they prefer to invest into driving everything through the ui. Software testability is the degree to which a software artifact i. If the testability of the software artifact is high, then finding faults in the system if it has any by means of testing is easier. Design for testability dft to overcome functional board. The purpose of manufacturing tests is to validate that the product hardware contains no manufacturing defects that could adversely affect the products. Usually failures are shorts between two conductors or opens in a conductor this can cause very complicated behavior a simpler model.
The following guidelines provide suggestions for improving the testability of circuits using xjtag. Everyone strives for 100% test coverage, but complete coverage is extremely difficult and expensive to achieve. The premise of the added features is that they make it easier to develop and apply manufacturing tests for the designed hardware. How single responsibility principle openclosed principle liskov substitution principle interface segregation principle dependency inversion principle. Need to test every bit in the register to make sure they all were fabricated correctly. Continuously shrinking process nodes have introduced new and complex onchip variation effects creating new yield challenges. Chapter 02 dft slides 091806 university of british columbia. Explain the meaning of the term design for testability dft.
Stuckat fault, delay fault, opens, bridges, iddq fault, fault equivalence, fault dominance, testing, method of boolean difference ps pdf. Conflict between design engineers and test engineers. Design for testability dft increases pincount or multiplexing of other ios order ing scan elements can reduce test time order ing scan elements can increase area or perf or mance costs te st mode mux selects scan. Measuring and improving design patterns testability. For the most part ok, it might be if you cut your programming teeth with microsofts rad tools, testability goes hand in hand with the same structural qualities like cohesion and coupling that we use to create code thats easier to write, change, and understand.
Combined with everincreasing design complexity with multiple memories, mixed signal blocks and ips from multiple vendors crammed into a single soc, design for test dft implementation and production test signoff has become a major challenge. Ieee xplore, delivering full text access to the worlds highest quality technical literature in engineering and technology. Design for testability dft refers to those design techniques that make test generation and test application costeffective electronic systems contain three types of components. This is usually done by measuring fault coverage, which is the percentage of the faults are covered by. Testability isnt some strange and unnatural new way to shape code. An interview with testing expert bret pettichord by sam guckenheimer senior director of technology for automated test rational software bret pettichord is an independent consultant in software testing and test automation as well as a coauthor, with cem kaner and james bach. Scan style, the most widely used structured dft methodology, tries to boost testability of a circuit by rising the controllability and observability of storage elements in an exceedingly sequential style.
Designfortestability features and test implementation of a giga hertz general purpose microprocessor article pdf available in journal of computer science and technology 236. Design for testability test for designability bob neal manufacturing test division agilent technologies loveland, colorado abstract. Testability in design build a number of test and debug features at design time this can include debugfriendly layout for wirebond parts, isolate important nodes near the top for facedownc4 parts, isolate important node diffusions this can also include special circuit modifications or additions. Lecture notes lecture notes are also available at copywell. Lecture 14 design for testability stanford university. If you design a testability feature, you probably won. How to design for testability dft for todays boards and systems presenter.
Vasily shiskin some applications are easy to test and automate, others are significantly less so. We use cookies to make interactions with our website easy and meaningful, to better understand the use of our services, and to tailor advertising. These suggestions will enable you to improve and add product test coverage to get the most out of boundaryscan testing. Testing 2 institute of microelectronic systems motivation stable chip manufacturing costs increasing testing costs. Next, this thesis also addresses the testability issues like test data volume, test time, and test power which scan inherits because of its serial nature. Design for testability scan chain insertion synopsys test compiler can automatically create a scan chain for you. Design for testability, agile testing, and testing processes. Synopsys can use scannable standard cells if your library has them or it can insert muxes for scanning. Security and testability issues in modern vlsi chips. Stuckat assume all failures cause nodes to be stuckat 0 or 1, i. This book is a comprehensive guide to new dft methods that will show the readers how to design a testable and quality product, drive down test cost, improve product quality and yield, and speed up timetomarket and timetovolume. The added features make it easier to develop and apply manufacturing tests to the designed hardware.
Therefore, a systematic and wellstructured approach to designing ics to be testable is a must. The potential advantages in terms of testability should be considered. Pcb defects guide design for test design for testability. Need some metric to indicate the coverage of the tests. Simulation, verification, fault modeling, testing and metrics. Dft is a general term applied to design methods that lead to more thorough and less costly testing. Test generation algorithms using heuristics usually apply some kind of testability measures to their heuristic operations e. Design for testability in digital integrated circuits. Design goal high cohesion low coupling good encapsulation 3.
Testability is a key ingredient for building robust and sustainable systems. You can specify the number of scan chains and even the order of the sequential elements in the scan chain. These guidelines should not be taken as a set of rules. What are the good books for design for testability in vlsi. How to design for testability dft for todays boards and. Designing for manufacturability and testability has been addressed by numerous publications and papers in the past. Testability committee to publish the smta testability guidelines in 2002 and helped in the project to revise it several times since. The ability to set some circuit nodes to a certain states or logic values. The potential advantages in terms of testability should be considered together with all other implications which they. Some of the proposed guidelines have become obsolete because of technology and test system. Ece 1767 design for test and testability outline computer.
Moreover, the proposed secure scan design techniques are very e cient in terms of design cost. Now, it is a wellknown fact in the software development industry that the earlier a bug is found, the cheaper it is to fix. Daasch, p or tland state univ ersity 7januar y 2015. Peter zimmerer describes influencing factors and constraints of designing software for testability and shares his experiences on the value and benefits of. Mah, aen ee271 lecture 16 8 testing testing for design. Functional vectors must be augmented by repeated use of a fault simulator. Normal mode mux selects data input scan data controls register contents r. To improve quality means more testing fault coverage more nets wiggled performance more nets wiggling at speed identify reliability risks soontofail devices competing interests between cost and quality.
Coverage of industry practices commonly found in commercial dft tools but not discussed in other books. Design for test design the chip to increase observability and controllability if each register could be observed and controlled, test problem reduces to testing combinational logic between. Logic simulation, 3value simulation, event driven simulation with delay consideration ps pdf fault modeling. Essentials of electronic testing for digital, memory and mixedsignal vlsi circuits, by m. Scan design is the most popular structured dft approach. Tck needs to be as free as possible of glitches and spikes, since all operations are triggered by rising and falling tck edges. Logic testing and design for testability 1 authors hideo fujiwara. Design for testability in digital integrated circuits bob strunz, colin flanagan, tim hall university of limerick, ireland this course was developed with part funding from the eu under the comett program. The most popular dft techniques in use today for testing the digital portion of the vlsi circuits include scan and scanbased logic builtin selftest bist. Makes internal circuit access much more direct to allow for controllability and observability converts a sequential test generation problem into a combinational test generation problem enables automatic test pattern generation enables automatic test pattern generation atpg enables use of lowenables use of lowpincount, low cost testers atepincount, low.
Mar 6, 2016 when designing a new software project, one is often faced with a glut of choices about how to structure it. Awta 2 jan 2001 focused on software design for testability. Design for testability dft has become an essential part for designing verylargescale integration vlsi circuits. Pdf design for testability of circuits and systems.