3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.1 General Structure Unit Under Test Data Compressor Data Generator Comparator Display Reference BIST Controller Start/StopReady Electronic System

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.2 Pattern Generator General Structure of an “n-1” Stage Linear Feedback Shift Register (LFSR).

3. 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. 3.2 Pattern Generator

3. 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. 3.3 Signature Generator Serial

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.3 Signature Generator r-Bit (Internal XOR) Signature Generator. The content of the LFSR is not the remainder of the division operation. Serial

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.3 Signature Generator Serial Example of a 4-Bit (External) Signature Generator.

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.3 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

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.3 Signature Generator Problem: fault masking When compacting results, there is a probability of fault masking ! Probability of failing to detect an error in the response sequence: Serial input Parallel input Where: K: length of the sequence (# of bits) r: length of the LFRS (# of bits) 2 mL- r – 1 2 mL – 1 2 k-r – 1 2 r – 1 Where: L: length of the sequence (# of test vectors) m: length of a vector (# of bits) r: length of the LFRS (# of bits)

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.4 Example: 8-bit-Length Datapath

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.4 Example: 8-bit-Length Datapath

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.4 Example: 8-bit-Length Datapath

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.5 Built-In Logic Block Observer (BILBO) Example of a “BILBO” structure.

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.5 Built-In Logic Block Observer (BILBO) Modular Bus-Oriented Design with “BILBO”.

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.6 Transparent BIST for Memory Test on the field Transparent Built-In Self Test is a test algorithm that is periodically executed on the field in order to verify the integrity of large amounts of critical data stored on mass memory systems

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.6 Transparent BIST for Memory Test Main characteristics: a)Minimum area overhead a) Minimum 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).

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.6 Transparent BIST for Memory Test Main characteristics: b)High capability of fault detection b) High capability of fault detection: by indicating the occurrence of stuck-at faults, transition faults,coupling faults, decoder faults and read/write logic faults.

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.6 Transparent BIST for Memory Test Main characteristics: c)Short “down times” c) Short “down times”: 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.

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.6 Transparent BIST for Memory Test Table 1. Signature Prediction Algorithm.  execution time

3. Built-In Self Test (BIST): Periodical Off-Line Test on the Field 3.6 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. Algorithm for Transparent BIST.  execution time