design for testability tutorial

Datum: 03.02.2014. hޜ�wTT��Ͻwz��0�z�.0��. This site uses Akismet to reduce spam. Place all JTAG devices into a single scan-chain and add test points for debug access—all JTAG devices are tested simultaneously in the serial chain. Design For Testability Design For Testability -- Organization Organization Overview of DFT Techniques AAd-d -hoc techniqueshoc techniques Examples I/O Pins Scan Techniques Full & Partial Scan C. Stroud 9/09 Design for Testability 1 Multiple Scan Chains Boundary Scan BuiltBuilt--In Self In Self--TestTest Evaluation Criteria for DFT Techniques . The methodology is called DFT; short for Design for Testability. At the QA&Test 2014 conference Peter gave a tutorial about design for testability for embedded software systems. endstream endobj 170 0 obj <> endobj 171 0 obj <> endobj 172 0 obj <>/Font<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 173 0 obj <> endobj 174 0 obj [/ICCBased 178 0 R] endobj 175 0 obj <> endobj 176 0 obj <> endobj 177 0 obj <>stream It's one of those vague non-functional requirements that are often neglected and wrongly ignored. You will work on DFT EDA and ATPG tools using special libraries on languages like Perl, Shell, or TCL. This often implies adding test points, but access improvements can be gained from many design activities. Design for testability (DFT) refers to those design techniques that make test generation and test application cost-effective Electronic systems contain three types of components: (a) digital logic, (b) memory blocks, and (c) analog or mixed-signal circuits In this chapter, we discuss DFT techniques for digital logic Definitions Very easy to implement, no design rule or constraints and area overhead is very less. But would you do it? Testing does not come for free. '�R�w�S���< xSt媆�����zw]��~`���q�Y�:b(�ɘ�Z��UYp?�5�ݦ/Z�ﺾ�:�p�M��� ����RF����Ԅ̆���k �嗢�FX)���õ��D�m����[7V �r�f$���Èc*��àV��I�"M#o۵e"��m�&����y� �}+���h� \���� `�r • This can also include special circuit modifications or additions. This methodology adds a bunch of features to test the chips. Hence, the count of verification engineers is also huge as compared to DFT engineers. The added features make it easier to develop and apply manufacturing tests to the designed hardware. ��[����A���eS�@56 Testability is increased by preventing anti-patterns like non-deterministic code, methods with side-effects, use of singletons, but use patterns like … With the increase in size & complexity of chips, facilitated by the advancement of manufacturing technologies, DFT has evolved as … Want a live explanation? The output also depends upon the state of the machine. With all these issues in mind, it becomes vital to test every chip before it can be shipped and in fact, test it after every level of manufacturing. This identifies the stage when the process variables move outside acceptable values. DFT Design for testability, sometimes calle d design for test and almost always abbreviated to DFT, is the philosoph y of considering at the design stage how the circuit or … Some of the proposed guidelines have become obsolete because of technology and test system advances. Modern microprocessors contain more than 1000 pins. We also saw an overview of what it entails and what’s to come in this course. Having introduced the first university course on Automatic Testing and Design for Testability at UCLA, he and his company have taught similar courses to thousands around the world in publicly held forums, at company facilities and online. Design For Testability -DFT course is a specialization in the SOC design cycle, which facilitates design for detecting manufacturing defects. DFT techniques are broadly classified into two types: These are a collection of techniques or set of rules (do’s and don’ts) in the chip design process learned from design experience to make design testability more comfortable to accomplish. Are the posts collapsed?Unable to see any content. In industry, this is done using formal verification processes like UVM (Universal Verification Methodology) using System Verilog. Uhrzeit: 10:00 - 13:00. Following are a few examples of structured DFT which we will cover extensively in future lessons: This was a short introduction to the concept of Design for Testability in VLSI. Prolonged overclocking would overheat and stress out your system to shorten the lifespan of your computer. System-level, when several boards are assembled together. Board-level, when chips are integrated on the boards. Maximum test coverage is achieved by testing all JTAG devices simultaneously. Designing for testability means designing your code so that it is easier to test. ⇒ Balanced between amount of DFT and gain achieved. Hs �*XD����C�eClÒ��9�&���£��c���0�,��8Dd��4\r�&��㱉����Vd``��W0p,�y � #Y�� It doesn’t guarantee high testability levels regardless of the circuit. 0000002006 00000 n To learn how that’s done, and everything it entails, keep up with the course! You need to have expertise in Verilog, System Verilog, C++. In simple words, Design for testability is a design technique that makes testing a chip possible and cost-effective by adding additional circuitry to the chip. JTAG Tutorial; I2C Tutorial; SPI Tutorial; BSDL Tutorial; Product Demos; Webinars; Whitepapers; Datasheets; Product Downloads; Training. Test access points must be inserted to enhance the controllability & observability of the circuit. Here are a few possible sources of faults: Faults can be classified into various subcategories. 0000001330 00000 n This is done either by increasing the number of nodes or by multiplexing existing primary outputs for the internal nodes to be observed. $O./� �'�z8�W�Gб� x�� 0Y驾A��@$/7z�� ���H��e��O���OҬT� �_��lN:K��"N����3"��$�F��/JP�rb�[䥟}�Q��d[��S��l1��x{��#b�G�\N��o�X3I���[ql2�� �$�8�x����t�r p��/8�p��C���f�q��.K�njm͠{r2�8��?�����. DFT (Design for Testability) involves using SCAN, ATPG, JTAG and BIST techniques to add testability to the Hardware design. Following are a few ad-hoc set of rules that designers generally follow: In this technique, extra logic and signals are added to the circuit to allow the test according to some predefined procedure. With design for testability being so important for complex designs, it helps to understand which test structures you should implement in your board for successful bare-board testing and ICT. Defect: Refers to a flaw in the actual hardware or electronic system. Successful testing and ISP of your design depends on a fully functional boundary-scan chain. So, how do we tackle this? De très nombreux exemples de phrases traduites contenant "design for testability" – Dictionnaire français-anglais et moteur de recherche de traductions françaises. • Examples: – DFT Errors in ICs are highly undesirable. Testability is the degree to which a system can be tested effectively and efficiently. �tq�X)I)B>==���� �ȉ��9. Others have been difficult to … 0 Please don’t! The authors wish to express their thanks to COMETT. 179 0 obj <>stream %%EOF Boundary-Scan Chain; Board Level Design; Improving Test Coverage; Improve Flash Programming Speed; JTAG Tutorials. Testing is applied at every phase or level of abstraction from RTL to ASIC flow. Join our mailing list to get notified about new courses and features. Testability in Design. – For wirebond parts, isolate important nodes near the top – For face-down/C4 parts, isolate important node diffusions. • In general, DFT is achieved by employing extra H/W. Avisekh has experience in FPGA programming and software acceleration. What is Design for Testability (DFT) in VLSI? endstream endobj 178 0 obj <>stream 0000001081 00000 n Tutorial on design for testability Abstract: Testability must be incorporated in all phases of an ASIC design, including wafer level, chip level, I/O level, and board/system level. Diagnosis: Process for locating the cause of misbehavior in the circuit if it happened. The purpose of manufacturing tests is to validate that the product hardware contains no manufacturing defects that could adversely affect the product's correct functioning. A chip may misbehave anytime if it is exposed to a very high temperature or humid environment or due to aging. In the pioneering of “Testability” (in 1964), and before acronyms such as DFT, DfT or DDT were established to describe specific segmented activities within the fully intended scope of “Designing for Testability”, the objective was to “Influence the Design for Testing” – any and all testing – AND concurrently, to influence the design for effective sustainment – “Design for sustainment”. By doing testing, we are improving the quality of the devices that are being sold in the market. Performed by simulation, hardware emulation, or formal methods. Tests … You should be able to access this now. DFT offers a solution to the issue of testing sequential circuits. 0000001215 00000 n trailer Both Verification and DFT have their importance in the VLSI industry. *A�$$@��M �]B�::�rL`#��R@����� 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. And to initialize them, we need a specific set of features in addition to the typical circuitry. The process is done after the RTL (Register Transfer Logic) design is coded with hardware description languages like VHDL or Verilog. Design for Testability: A Tutorial for Architects and Testers. This technique is the only solution to modern world DFT problems. 0000000516 00000 n the “Design for Testability” standards. About the authorAvisekh GhoshAvisekh is currently pursuing B.Tech in Electrical Engineering from Delhi Technological University. This is performed only once before the actual manufacturing of chip. It’s kind of hard to test sequential circuits. 0000000016 00000 n What is Design for Testability, and why we need it? Here are a few terminologies which we will often use in this free Design for Testability course. Smaller die sizes increase the probability of some errors. He has served on international standards committees, such as the IEEE. Verification proves the correctness and logical functionality of the design pre-fabrication. Design for testing or design for testability consists of IC design techniques that add testability features to a hardware product design. %PDF-1.4 %���� We may need to test every functionality with every possible combination. By testing a chip, vendors try to minimize the possibility of future errors and failures. An improperly configured overclocking can mess up with timing metrics and cause instability. This may cause intermittent faults in the chip and random crashes in the future. 169 11 To do so, you may have to break with some of the principles we learned in university, like encapsulation. Read our privacy policy and terms of use. He is a front-end VLSI design enthusiast. However, new technologies come with new challenges. Read the privacy policy for more information. To ensure the highest quality of chips, there is also an auxiliary process involved in the chip-design process called Verification. This saves time and money as the faulty chips can be discarded even before they are manufactured. Boundary-Scan Chain Design for Testability. Meticulous monitoring improves process-line accuracy and decreases the fault occurrence probability. 17: Design for Testability Slide 7CMOS VLSI Design Manufacturing Test A speck of dust on a wafer is sufficient to kill chipA speck of dust on a wafer is sufficient to kill chip Unlike combinational circuits, we can’t determine the output of sequential circuits by merely looking into the inputs. These errors can be costly in more ways than just financially. Testability is the degree to which a system can be effectively and efficiently tested. Design for Testability Tips. The key takeaway is just that there is a lot of room for error in the manufacturing of ICs. Design for Testability Engineers; Design Engineers; Custom Circuit Designers; Chip Designers; Cadence Application Engineers; ASIC Designers; CAD System Administrators; CAD Engineers; This class is open to anyone with a curiosity about the basics of testing digital ICs. Hence, the state machines cannot be tested unless they are initialized to a known value. Design-for-Test techniques for improving PCB testability using JTAG Boundary Scan, resulting in faster test development, lower cost manufacturing test For becoming a Verification expert, you have to gain experience practically (not theoretical much). You will work closely with physical design engineers and RTL design engineers. No, faults can arise even after the chip is in consumer’s hands. The purpose of manufacturing tests is to make ATPG easier. So, does testing guarantee that the chip will never be faulty again? 0000001969 00000 n This demands analytical and software programming skills, along with hardware skills. Testing is carried out at various levels: There is an empirical rule of thumb that it is ten times more expensive to test a device as we move to the next higher level (chip → board → system). 12: Design for Testability 5CMOS VLSI DesignCMOS VLSI Design 4th Ed. Testing: An experiment in which the system is put to work and its resulting response is analyzed to ascertain whether it behaved correctly. For the Verification domain, you will work in design development and some of the advanced constrained random test benches. These subjects will play a significant role in your day-to-day work. Fault Coverage: Percentage of the total number of logical faults that can be tested using a given test set T. Defect Level: Refers to the fraction of shipped parts that are defective. He is working on the implementation of digital systems targeting the most recent advances in computation like Machine Learning, Information Security and Reconfigurable Computing. If you have an unlocked processor, you can try to overclock your CPU using this tutorial. This is an introduction to the concepts and terminology of Automatic Test Pattern Generation (ATPG) and Digital IC Test. startxref It is done using a testbench in a high-level language. The premise of the added features is that they make it easier to develop and apply manufacturing tests for the designed hardware. By signing up, you are agreeing to our terms of use. Test application is performed on every manufactured device. where Y is the yield, means the fraction of the chips fabricated that are good. Fault Modeling in Chip Design – VLSI (DFT), Fault Collapsing methods and Checkpoint Theorem in DFT (VLSI), Automatic Test Pattern Generation (ATPG) in DFT (VLSI), D algorithm – Combinational ATPG in DFT (VLSI), Internal Scan Chain – Structured techniques in DFT (VLSI), Introduction to JTAG Boundary Scan – Structured techniques in DFT (VLSI). Qf� �Ml��@DE�����H��b!(�`HPb0���dF�J|yy����ǽ��g�s��{��. ".�T����}t��gs �>���X�=�� 8�-0 This is accomplished by improving Observability and Controllability attributes. )ɩL^6 �g�,qm�"[�Z[Z��~Q����7%��"� Fault: It is a model or representation of defect for analyzing in a computer program. Large circuits should be partitioned into smaller sub-circuits to reduce test cost. There tests in turn help catch manufacturing defects like stuck at 0, 1 faults, and transition delay faults etc. Since there are clocks involved along with the flip-flops. If testing is done that way, then the time-to-market would be so high that the chips may never reach the consumers. DFT accomplishes two significant goals in the chip manufacturing process: Testing checks the errors in the manufacturing process that are creating faults in the chips being designed. They pack a myriad of functionalities inside them. Implementing the right design for testability practices takes the right design software and documentation. A chip can’t ever be made resistant to faults; they are always bound to occur. The possibility of faults may arise even after fabrication during the packaging process. Here’s a list of some possible issues that arise while manufacturing chips. This is the highest level of abstraction in the VLSI industry, and there’s a lot of degree-of-freedom on your side to verify the design. The way the code is structured can have a great impact on how good the code can be unit tested. The point is, you can even generate a fault on your own. His future aspirations are contributing to open source silicon or hardware development community as well as CAD tools. In contrast to Ad-hoc, structured DFT implies that the same design approach can always be used and assure good testability levels, regardless of the circuit function. He is a front-end VLSI design enthusiast. ��?�]�4�R��"lĎ6��;d�m�;9�^�^�F����P5�f��^p� E Today, semiconductors lie at the heart of ongoing advances across the electronics industry. Applying these rules and suggestions during the board designing process allows getting a more complete and less expensive test. The career path might be more aligned to the backend/physical design and would have to deal with the complexities and challenges of newer technologies. Basically, these are the rules that have been gathered over time after experiencing various errors. As we move to higher levels, more components are integrated, which makes the fault detection and localization much more difficult and expensive. 169 0 obj <> endobj Design for Testability or DFT is a name for design techniques that add certain testability features to a microelectronic hardware product design. He is working on the implementation of digital systems targeting the most recent advances in computation like Machine Learning, Information Security and Reconfigurable Computing. Tutorial on design for testability (DFT) "An ASIC design philosophy for testability from chips to systems" Abstract: This is a comprehensive tutorial on DFT with emphasis on concepts of digital Application Specific Integrated Circuit (ASIC) testing incorporating boundary scan architecture in ASIC design. Silicon Debug Test the first chips back from fabrication – If you are lucky, they work the first time – If not… Logic bugs vs. electrical failures – Most chip failures are logic bugs from inadequate simulation – Some are … Testing needs to be performed on each manufactured chip because each one of them has an equal probability of being faulty during the fabrication or packaging process. Design for testability (DFT) has migration recently – From gate level to register-transfer level (RTL) VLSI Test Principles and ArchitecturesEE141 Ch. xref Most verification engineers don’t get involved in circuits, transistors, or backend design part. To reduce these errors significantly, a methodology known as DFT exists. All rights reserved. Design for Testability – Test for Designability Bob Neal Manufacturing Test Division Agilent Technologies Loveland, Colorado Abstract: Designing for manufacturability and testability has been addressed by numerous publications and papers in the past. Document rescued from the depths of internet. About 2/3rd of VLSI design time is invested in the verification process, thereby making it the most time-taking process in VLSI design flow. "Essentials of Electronic Testing for Digital, Memory and Mixed-Signal VLSI Circuits", by M. L. Bushnell and V. D. Agrawal, is often thought of as the Bible for DFT. 0000003510 00000 n Sprecher: Peter Zimmerer . Alternatively, Design-for-testability techniques improve the controllability and observability of … So, what are we trying to achieve? x�b```f``�d`a``Y� Ȁ �@16 �``p�PP�a``_�����`Bf�ڜw,���ev�ߙ��Y~���L~ߩL�K'r,S���9o��Ϊ_�K��3dir�qh�2{��6YxX@�C�R�C�DC&QS�8Hͥ�T���a♓�6P�����ف�T~�,��4{��)����Ы 1���1���?P%X�H0������QD2�F00��5 �آH�e00 ��BJ�pp 0000002230 00000 n Testing a device increases our confidence. �V�����1�ï�Re�Fqo�M� ��uс[o�T��.��;t�Y/�o7�׮,= @�7�a�=5�DX����5��wh���G'a�]�\�kTu���z�T�o`�!�~@���c��!������jM2qp>O��к�x�g�6��w�v���5U�ô�ҖA=��P�A�P�#�BF��V���2S�T��������{�>�Oʍ�OƼ��s�:i��p�� ���n��� �6�uu� ���������5�� �܇Z Usually, design for testability (DFT) techniques are applied down to the logic design level, and test patterns are generated to cover single line stuck-at (LSA) faults. These techniques are targeted for developing and applying tests to the manufactured hardware. In contrast, testing tries to guarantee the correctness of the manufactured chips at every abstraction level of the chip design process. Thank you for bringing this to our attention! Test and Design for Testability of Analog and Mixed-Signal Circuits ACEOLE - PH-ESE Electronics Seminars 4-5 February 2010 José Machado da Silva U.Porto – Faculdade de Engenharia INESC Porto. Scan-Chain. 0000000996 00000 n This has brightened the prospects for future industry growth. This simplifies failure analysis by identifying the probable defect location. In simple words, Design for testability is a design technique that makes testing a chip possible and cost-effective by adding additional circuitry to the chip. To do so, you may have to break with some of the principles we learned in university, like encapsulation. <]>> We use a methodology to add a feature to these chips. Designing for testability in a PCB design (DFT) is a critical step in the design for manufacturability (DFM) process. Verification is a vast topic on its own and we will cover it in this VLSI track and link it here soon. What is the difference between Verification and Testing? Let’s segue into the career aspect of these two stages for a moment. This critical concept boils down to developing a consistent product for the lowest possible manufacturing cost while maintaining an acceptable rate of defects. The diagnostic software module provides the industry’s most robust diagnostic design and analysis tools. For DFT, you need to be good at CMOS VLSI, Digital Electronics, Testing of Digital Circuits, Verilog, and a little bit of scripting knowledge. They only deal in the frontend domain. Avisekh has experience in FPGA programming and software acceleration. Design for Testability 13 Design for Testability (DFT) • DFT techniques are design efforts specifically employed to ensure that a device in testable. 0000002308 00000 n Both of them have an excellent scope, as you see from the product development perspective. If any single transistor inside a chip becomes faulty, then the whole chip needs to be discarded. h޼V�n�6��S�K���S�͆�A�"�YC.�^0�⨵�D�k��Q`{���)ɱ�&� #1#�������GJ��%\(0Z�LI�J�-�BR¤����^AQ0�*@3)��|q:�4,:`��-���9�U7��\C;�A�����yt��k�7�&�1 ?�g��1�R��A^!�U�J�0�m�!>;a\�~�&�! If you are working as a DFT engineer, then your team size will be much smaller as compared to the verification team. Anyone involved in digital IC design or support can benefit from it. You can choose any one of them, depending upon your subject of interest. Error: It is caused by a defect and happens when a fault in hardware causes line/ gate output to have a wrong value. There is, however, a price to pay, which usually consists of accepting that some design rules (rather a design style) are enforced and that additional silicon area and propagation delays are tolerated. ⇒Conflict between design engineers and test engineers. If faults can be detected earlier, then the underlying process causing the faults can be discarded at that point. Verification is performed at two stages: Functional Verification and Physical Verification. • Build a number of test and debug features at design time • This can include “debug-friendly” layout. DFT enables us to add this functionality to a sequential circuit and thus allows us to test it. And the feature it adds to a chip is ‘testability.’. Overclocking is a method to increase the system frequency and voltage above the rated value. Are not always reusable, since each design has its specific requirements and testability problems. ���#���=��Sd�+�0J�䰨��*�B-8���|?���+��L���H�1I��5�z�x | �6�ȳIR��m�'6��*K�ןB��B��,�?E�-���c�9�d��Hf��tr��#� Verifies correctness of the manufactured hardware. Don’t fret if you can’t completely understand them yet, we will be covering them in-depth in this course. Avisekh is currently pursuing B.Tech in Electrical Engineering from Delhi Technological University. Design for Testability (DFT) techniques are effective ways to reduce FBT test programming complexity. ��3�������R� `̊j��[�~ :� w���! Vortrag: Mo 7. Prerequisites. Level-sensitive scan design (LSSD) is a design technique that uses latches and flip-flops that are level sensitive as opposed to edge triggered. Designing for testability means different things for each phase in testing. Nonetheless, this document contains not binding rules and suggestions that make possible, for the designer, to test the board in the best possible way and in total freedom. But identifying that one single defective transistor out of billions is a headache. Adding to this, it may void your warranty too. Or, the proportion of the faulty chip in which fault isn’t detected and has been classified as good. The introduction of new technologies, especially nanometre technologies with 14 nm or smaller geometry, has allowed the semiconductor industry to keep pace with increased performance-capacity demands from consumers. $E}k���yh�y�Rm��333��������:� }�=#�v����ʉe It is difficult to control and observe the internal flip-flops externally. Alternatively, Design-for-testability techniques improve the controllability and observability of internal nodes, so that embedded functions can be tested. This key software attribute indicates whether testing (and subsequent ma… o�y��C�Ì�E4�$,6���� cI���Q��L�W�P5�����c�SD�?`�R���[fDY\!�"���2�l�Ɛ/ղ^�kו�bo����1b�d����Y>��;I�ET�c���^²�ެ��a�TU�.J��n���R@��ܹ���!2>`���c�iE��{��$3u�'I�E7�#v�zX6p�!�j�h���� Sequential circuits consist of finite states by virtue of flip-flops. This example is just one high-level explanation of how a fault may occur in real life. We, consumers, do not expect faulty chips from manufacturers. Not systematic enough to enable a uniform approach to testable circuit design. Failure: This occurs when a defect causes misbehavior in the circuit or functionality of a system and cannot be reversed or recovered. His future aspirations are contributing to open source silicon or hardware development community as well as CAD tools. For unit tests and developer tests the main focus will be on the design of code. Learn how your comment data is processed.

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