Logic Analyzers

Failure analysis or fault finding in electronic systems, especially those involving digital circuits, can be a very dreary task. Logic analyzers are used in such cases where the data in digital form is captured from the system and is then used to analyze the faults in the system. The processing of digital circuits is much too fast to be noticed by the human eye and so most of the errors or faults are not traceable. Additionally, too many channels or signals need to be examined at a time, which is a difficult task. Logic analyzers are used in cases that present the digital data to the user, who can carry out further analysis.

The system being tested triggers a sequence of digital pulses when some error condition occurs. The logic analyzer is then activated after receiving these pulses and digital information is copied from the system under test, to trace the error point precisely. A logic analyzer therefore would trigger on a complicated sequence of digital events, and then it will copy a large amount of digital data from the system that is being tested.

Logic analyzers basically behave more or less like software debugging systems. Digital systems today are equipped with built-in debuggers, which trace the defects and faults, at the time of fabrication itself. However, external logic analyzers are still in use today for their high-speed data capture and exact reproduction features.

When logic analyzers were first used, several hundred "clips" were usually attached to a digital system. Later on, specialized connectors became popular. In most modern computer systems assorted other tools have now made logic analyzers obsolete for many of their uses. For instance, many microprocessors have hardware support for software debuggers. Many digital designs, including those of ICs, are simulated to detect defects before the units are built. The simulation usually provides logic analysis displays. Often, complex discrete logic is verified by simulating inputs and testing outputs using boundary scan. However, none of these will duplicate the exact high-speed data capture function of a logic analyzer however they cover most real needs for debugging digital circuits.


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