engineering

Logic built-in self-test

Logic built-in self-test is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Logic built-in self-test rather than just read about it. In short: Logic built-in self-test (or LBIST) is a form of built-in self-test (BIST) in which hardware and/or software is built into integrated circuits allowing them to test their own operation, as opposed to reliance on external automated test equipment. Advantages The main advantage of LBIST is the ability to test internal circuits having no direct connections to external pins, and thus unreachable by external automated te…

Key takeaways

Logic built-in self-test belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Logic built-in self-test to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Logic built-in self-test from memory before moving on to harder problems.

Reference excerpt

Logic built-in self-test (or LBIST) is a form of built-in self-test (BIST) in which hardware and/or software is built into integrated circuits allowing them to test their own operation, as opposed to reliance on external automated test equipment.

Advantages The main advantage of LBIST is the ability to test internal circuits having no direct connections to external pins, and thus unreachable by external automated test equipment. Another advantage is the ability to trigger the LBIST of an integrated circuit while running a built-in self test or power-on self test of the finished product.

Disadvantages LBIST that requires additional circuitry (or read-only memory) increases the cost of the integrated circuit. LBIST that only requires temporary changes to programmable logic or rewritable memory avoids this extra cost, but requires more time to first program in the BIST and then to remove it and program in the final configuration. Another disadvantage of LBIST is the possibility that the on-chip testing hardware itself can fail; external automated test equipment tests the integrated circuit with known-good test circuitry.

Related technologies Other, related technologies are MBIST (a BIST optimized for testing internal memory) and ABIST (either a BIST optimized for testing arrays or a BIST that is optimized for testing analog circuitry). The two uses may be distinguished by considering whether the integrated circuit being tested has an internal array or analog functions.

See also Built-in self-test Built-in test equipment Design for test Power-on self-test

External links Built-in Self Test (BIST) "Embedded Processor Based Built-In Self-Test and Diagnosis". CiteSeerX 10.1.1.94.3451. {{cite web}}: Cite uses deprecated parameter |citeseerx= (help); Missing or empty |url= (help) Hardware Diagnostic Self Tests BIST for Analog Weenies

Worked examples

Example 1 — a first encounter with Logic built-in self-test

Start with the simplest possible case. Write down what Logic built-in self-test claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Logic built-in self-test before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Logic built-in self-test ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Logic built-in self-test

In research: Logic built-in self-test appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Logic built-in self-test in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Logic built-in self-test is common in secondary-school and first-year university syllabi. It links to neighbouring topics Integrated circuits, so understanding it makes those chapters shorter.
In everyday life: Look for Logic built-in self-test outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Logic built-in self-test in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Logic built-in self-test means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Logic built-in self-test out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Logic built-in self-test in simple terms?

Why does Logic built-in self-test matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Logic built-in self-test?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Logic built-in self-test.