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Reducing False Alarms and System Aborts

FA’s and FSA’s and BIT Effectiveness

While there is plenty of leeway for interpretation or the meaning of a False Alarm (FA) as it may pertain to any particular industry or event, we will consider the FA to be the result of an incorrect indication of a “failure” as observed and reported by any sensing device. Furthermore, we will define that sensing device to be a Built-In-Test (BIT) or any other monitoring circuity or sensor. Before we jump ahead to learn about the significant what impact a well-executed diagnostic design process has on either FAs or System Aborts (SA), we will first examine BIT.

Complex equipment, vehicles, or systems today use many forms of BIT. The BIT used can serve to instantly and dynamically test the circuitry at any specific time during the operation of the equipment, vehicle or system. Specific sets of BIT can be used at different points in time to quickly examine if the relevant, specific operational functions contained within that set are operating correctly. Consequently, the purpose of BIT is to report back to the operator that everything that it examined is operating as expected.

If we are interested in discovering whether we are able to start up our system or vehicle, then it usually is designated as Start Up Built-In-Test (SBIT). Some programs may instead designate this SBIT as Performance BIT (PBIT), but it essentially serves the same specific purposes as SBIT. In fact, there are many types of BIT such defined such as those defined in the table below.

Various Types of Built-In-Test (BIT) Classifications and Definitions

There are other forms of BIT that are more prevalent today in the semiconductor industry that address the piece parts of lower-level designs. These indeed can ultimately be captured and included in higher-level diagnostic designs using eXpress and Integrated System Diagnostic Design (ISDD) methodology. For example, BIT or BIST refer to a specific form of test in which hardware and/or software is built into integrated circuits, thereby allowing them to perform sophisticated self-testing of their own operation. That approach is contrary to the reliance on external Automated Test Equipment (ATE). That includes other related forms for similarly targeted BIT, such as LBIST, MBIST, ABIST, which would be used to test, respectively read-only memory, internal memory, or arrays of memory. However, we will be discussing only the use of higher level BIT as described below.

Fault Detection is the First Step – Fault Isolation is the Value Target

While the vast majority of the semiconductor industry is embarking on many forms of advanced applications for BIST; it hasn’t been conscious of moving beyond Fault Detection (FD) realm. In other words, the awareness of being able to observe the loss of any function, is only assurance of FD and has no objective to determine the root cause of the detected failures through Fault Isolation (FI). Again, this is the major difference between FD and FI, or diagnosis.

Investment is sometimes made into the use of the BIST technologies but not as often as it should. This is In part because the benefit at the fielded-product level is not maximized until, or unless, the BIST can be captured and fully integrated into the fielded-product for increased and ongoing sustainment value. This is precisely why eXpress and ISDD need to be employed to capture the lower-level test detail to be used for:

  • Injecting diagnostic acumen into the ATE for production testing with diagnostic capabilities
  • Integrating diagnostic acumen into the fielded-product embodying and leveraging these lower-level designs

Related Links

Influence the Design for DFT
Influence the IVHM Design for Enhanced Sustainment Capabilities

Related Documents and Videos

Technical Brief – Built-In-Test, A Designers Handbook
Diagnostic Validation through Fault Insertion
COTS-Based Solution for Through-Life Support

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