4 . built-in self test (bist): periodical off-line test on the field

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.1 General Structure

UnitUnder

Test

DataCompressor

DataGenerator

Comparator

Display

Reference

BIST ControllerStart/Stop Ready

Electronic System

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.2 Pattern Generator

General Structure of an “n-1” Stage Linear Feedback Shift Register (LFSR).

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

Example of a 4-Bit LFSR as a Pattern Generator.

Pseudorandom States Generated by the LFSR.

4.2 Pattern Generator

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

r-Bit (Internal XOR) Signature Generator. The content of the LFSR is the remainder of the division operation.

4.3 Signature Generator

Serial

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.3 Signature Generator

r-Bit (External XOR) Signature Generator. The content of the LFSR is not the remainder of the division operation.

Serial

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.3 Signature Generator

Serial

Example of a 4-Bit (External) Signature Generator.

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.3 Signature Generator

r-Bit (Internal XOR)

Parallel Signature Generator.

The content of the LFSR is not the remainder of the division operation.

r-Bit (External XOR)

Parallel Signature Generator.

The content of the LFSR is the remainder of the division operation.

Parallel

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.3 Signature Generator

Problem: Problem: When compacting results, there is a probability of fault maskingfault masking !

Probability of failing to detect an error in the response sequence:Probability of failing to detect an error in the response sequence:

Serial inputSerial input Parallel inputParallel input

Where: K: length of the sequence (# of

bits)r: length of the LFSR (# of bits)

2mL- r

– 1

2mL

– 1

2k-r

– 1

2r – 1

Where: L: length of the sequence (# of test

vectors)m: length of a vector (# of bits) r: length of the LFSR (# of bits)

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.4 Example: 8-bit-Length Datapath

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.4 Example: 8-bit-Length Datapath

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.4 Example: 8-bit-Length Datapath

Signature Generator (External XOR).

Parallel Pattern Generator (External XOR): all inputs Z’s equal to “0”.

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.5 Built-In Logic Block Observer (BILBO)

Example of a “BILBO” structure.

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.5 Built-In Logic Block Observer (BILBO)

Modular Bus-Oriented Design with “BILBO”.

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.6 Transparent BIST for Memory Test

Transparent Built-In Self Test is a test

algorithm that is periodically executed

on the fieldon the field in order to verify the

integrity of large amounts of critical

data stored on mass memory systems

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.6 Transparent BIST for Memory Test

Main characteristicsMain characteristics::

a)a) Minimum area overheadMinimum area overhead: this approach is one of the

best choices found in the literature in terms of area

overhead and types of faults detected in memory

structures. E.g., authors claim an area overhead of 1.2%

due to the inclusion of Transparent BIST in a 128Kbytes

X 8bytes SRAM (this value decreases as the RAM size

increases).

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.6 Transparent BIST for Memory Test

Main characteristicsMain characteristics::

b)b) High capability of fault detectionHigh capability of fault detection: by indicating the

occurrence of stuck-at faults, transition faults, coupling

faults, decoder faults and read/write logic faults.

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.6 Transparent BIST for Memory Test

Main characteristicsMain characteristics::

c)c) Short “down Short “down timestimes””: that are periodically required to

check the functionality of mass memory systems used

in real-time applications. The Transparent BIST

approach presents the incomparable advantage of

preserving the contents of the RAM memory after

testing. Thus, this approach is very suitable for periodic

testing since we do not need to save the memory

contents before the test session and to restore them at

the end of this session.

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.6 Transparent BIST for Memory Test

Table 1. Algorithm for Transparent BIST.Table 1. Algorithm for Transparent BIST.

execution time

4. Built-In Self Test (BIST):Periodical Off-Line Test on the Field

4.6 Transparent BIST for Memory Test

Note that the data read during the execution of sequences S1’ through S4’ of the signature prediction algorithm (Table 2) are sometimes inverted in order to match the data read during the execution of sequences S1 through S4 of the Transparent BIST (Table 1).

Table 2. Signature Prediction Algorithm.Table 2. Signature Prediction Algorithm.

execution time

S1 S2 S3 S4 R1 R1 R1 R1 R1 R1 R2 R2 R2 R2 R2 R2 ... ... ... ... ... ... ... ... Rn Rn Rn Rn Rn Rn