Logic Analyzer : Block Diagram, Working, Types, Differences, Maintenance & Its Applications

Analyzing various digital signals simultaneously has become essential in digital technology to identify and resolve design flaws and operational problems. Engineers developed logic analyzers as essential tools when the earliest microprocessors entered the market. They discovered that these analyzers effectively addressed the debugging challenges posed by complex digital systems in microprocessors. This essential tool helps engineers who design many digital circuits in design verification, embedded software debugging, and digital hardware debugging. This article elaborates on a logic analyzer, its working, and applications.

What is a Logic Analyzer?

A logic analyzer is a versatile tool similar to many measurement and electronic test tools that capture & display various logic signals from a digital circuit or digital system. This analyzer may change the captured logic signals into timing diagrams, state machine traces, and protocol decodes, and may associate op-codes with source-level software. These have higher triggering capabilities and are helpful whenever a user needs to observe the timing relationships between various signals within a digital system.

Some logic analyzers can detect glitches & set and hold time violations to debug intermittent problems. In software and hardware integration, these analyzers can trace the implementation of embedded software and examine the efficiency of its execution within a program. Some logic analyzers compare the source code with particular hardware activities within your design.

Logic Analyzer Block Diagram

The logic analyzer basic functional block diagram is shown below.

Probes

Logic analyzer probes are the physical connections that are frequently simple, small circuitry or a wire piece with a clip. It helps in connecting a logic analyzer to the electronic circuit under test by allowing the analysis and capture of digital signals. Probes are available in different forms like test points, specialized connectors, and flying lead probes, where each has different characteristics & is suitable for specific applications. The selection of a proper probe and its setup is essential for precise measurements and consistent repair of digital systems.

Clock Select

Some types of logic analyzers let you choose which clock to use for testing the signals. An internal clock will test the signals at regular intervals, or you can use an input channel as the clock source.

Comparator

The logic analyzer compares every input signal to a personalized voltage threshold, not like an oscilloscope. If the voltage is higher than to threshold, then it is stored as a logic high or else it is stored as a logic low. Logic analyzers do not need ADCs, but they frequently have a lot of channels as compared to oscilloscopes.

Trigger Logic

Logic analyzers regularly have more triggering features as compared to oscilloscopes. All of the explored channels can be utilized to activate the start of capture, and some superior logic analyzers will allow you to design complex triggers through if-then-else statements.

Trigger Select

Some logic analyzers allow you to choose between triggering from the separate trigger input or capture channels. So this specialized input is used to synchronize other test equipment, like an oscilloscope.

Memory

Logic analyzers have memory in the chassis of the logic analyzer, which stores the captured sequence of logic 0s and 1s in memory.

Display

Waveforms representing the captured digital signals can be drawn for the user on a display. Related to an oscilloscope, the X-axis for every waveform is time, and the Y-axis for every waveform can be voltage. If the voltage is logic high, then the voltage is above a threshold; otherwise, the voltage is below it.

How Does a Logic Analyzer Work?

A logic analyzer works by capturing and displaying the timing and performance of various digital signals within a digital circuit. First, it samples the signal’s voltage levels at regular intervals and signifies them as 0s and 1s. After that, it is analyzed the timing relationships between various signals are analyzed, debugging digital circuits & confirming the functionality of digital systems.

The steps involved in working with a logic analyzer are discussed below.

Signal Capture:

A logic analyzer connects various test points in an electronic circuit using probes. These probes are mainly designed to detect the high or low logic levels of the digital signals. The analyzer can sample the signals at a predefined rate by efficiently taking the voltage level’s snapshots at standard intervals.

Acquisition & Storage of Data:

The sampled data is represented as binary data and is stored within the memory of the logic analyzer. Here, the memory depth decides how long the logic analyzer can trace data before requiring resetting or re-triggering. Several logic analyzers can also provide triggering capabilities by allowing users to identify certain conditions that should be met before starting data acquisition.

Display & Analysis

Finally, the captured data can be displayed on the screen of the analyzer frequently in the shape of timing diagrams. These diagrams signify the signal changes visually, eventually making it easy to recognize timing glitches, issues, and other differences. These analyzers can also decode complex digital protocols to display them in a readable format.

Specifications

The logic analyzer specifications mainly include the following.

• A logic analyzer includes several channels that range from a few channels to a hundred.
• Timing mode captures signal changes at a high sampling rate, which is useful to analyze timing relationships & also detect glitches.
• A logic analyzer in state mode captures logic states at particular clock edges, which is useful to analyze data transfers & protocol performance.
• It is measured in 12.5 GHz to determine how fast the analyzer captures signal transitions.
• State data rates indicate the highest data rate at which the analyzer can capture synchronized data to a CLK signal, also frequently expressed in 4 Gb/s.
• The memory depth of the analyzer is the amount of data that it can store, like 2 MB for standard and up to 256 MB within half-channel mode.
• These analyzers can be arranged with complex trigger forms to capture particular events (or) sequences of signals.
• It supports different protocols like I2C, SPI, DDR & USB.
• It uses high-resolution-based large displays to view & analyze signals very easily.
• Its probes can affect measurement accuracy & signal integrity.
• This logic analyzer software provides some features like packet lists, analysis tools & protocol decoding.

Types of Logic Analyzer

Logic analyzers are available in three types: modular logic, portable logic, and PC based, which are explained below.

Modular Logic Analyzer

A modular logic analyzer is the standard type and an expensive device observed in labs. It includes a mainframe & various modules, where each module includes a specific number of channels and provides the highest level functionality to the user. This instrument is mainly designed to capture, display & examine digital signals within difficult electronic systems. The module can be added or eliminated in the logic analyzer based on the user to enhance the number of channels and functionality.

The benefits of a logic analyzer are: higher performance, high channel count ability, and more features. The drawbacks are: expensive, less portable, etc.

Portable Logic Analyzer

A portable logic analyzer is a kind of electronic test instrument utilized to capture & analyze digital signals in electronic circuits or systems. This self-contained unit includes displays &controls that make them to use in on-site troubleshooting & debugging. These analyzers frequently include some features like timing, state analysis & triggering capabilities.

The advantages of a portable logic analyzer are: convenient for testing & troubleshooting. The drawbacks of this analyzer include a smaller channel count & fewer advanced features.

PC-based Logic Analyzer

A PC-based logic analyzer is a compact unit that is connected to a computer frequently through USB/Ethernet. It uses the display of computers, processing power & storage to capture and analyze digital signals. This logic analyzer relies on a connected PC for its user interface & processing capabilities instead of having its own dedicated display & processing unit.

The benefits of PC PC-based logic analyzer are the most affordable, very compact & portable. The drawbacks are: fewer advanced features and limited performance.

Logic Analyzer Vs Oscilloscope

Logic analyzers & oscilloscopes are both fundamental tools to analyze electrical signals; however, they focus on different features. The difference between a logic analyzer and an oscilloscope includes the following.

Logic Analyzer Vs Spectrum Analyzer

A logic analyzer and a spectrum analyzer are both electronic test instruments, but they serve different purposes. Below, we discuss the key differences between these two analyzers..

Maintenance

Logic analyzer maintenance involves various steps to ensure precise and consistent operation.

• Understanding these steps is significant to get good performance.
• Maintain the logic analyzer device with its probes very clean from debris and dust.
• Avoid using solvents or harsh chemicals that could harm the device.
• The logic analyzer must be stored in a dry or cool place and kept away from direct extreme temperatures or sunlight.
• Place the device in a protective case or its original packaging to avoid damage in storage.
• Make sure proper grounding with the smallest ground connection for every two signals with flying lead probes.
• Probe wires must be maintained properly to reduce signal reflections & develop signal integrity.
• Use the suitable type of probe for your application. So, low-capacitance probes are used for high-speed systems.

Calibration

• Some logic analyzers include a self-calibration feature that must be run occasionally.
• After calibration, check the analyzer’s accuracy with a calibration standard or known test signals.

Software:

• Keep the software of the logic analyzer up-to-date to profit from new features and bug fixes.
• Know the features & capabilities of software to optimize your workflow.
• Select the correct software for your requirements for Keysight’s software or open-source projects for superior features.

Advantages

The advantages of a logic analyzer include the following.

• A logic analyzer measures multiple signals simultaneously and shows their relative timings.
• They capture high-speed signals.
  This analyzer displays the captured data in ASCII, binary, hexadecimal, or decimal.
• You can set it to activate on specific events or patterns.
• Engineers find logic analyzers to be inexpensive tools for correcting embedded systems, using them to check communication between peripherals, microcontrollers, and more.
• The logic analyzer provides configurable sampling rates, acquisition durations, and channel counts, enabling modifications for a wide range of debugging scenarios.
• Logic analyzer captures and analyzes signals at very high speeds to make them perfect for high-speed digital circuits.
• These analyzers provide complicated triggering capabilities by allowing users to capture information based on specific patterns or conditions.
• They decode a variety of digital communication protocols to understand easily & correct data transfers.
• Many types of logic analyzers provide both timing and state analysis modes.
• Logic analyzers can incorporate oscilloscopes by allowing for time-correlated and cross-triggering display of both signals.
• They identify and diagnose issues related to crosstalk, signal integrity, and signal reflection issues.

Disadvantages

The disadvantages of a logic analyzer include the following.

• Logic analyzers can be expensive due to principally high sampling rates and channel counts.
• They also measure logic levels and not current or voltage, which can be a drawback in some applications.
• These are not suitable for analyzing high-speed or analog signals, where an oscilloscope or dedicated peripheral is more suitable.
• Logic analyzers mainly focus on digital signals for measuring high or low voltage levels.
• Logic analyzer configuration is challenging, principally for those not familiar with the device & its software.
• Its usage is limited in some applications.
• It may need external wires or probes.
• Some logic analyzers need separate hardware/probes to capture both state and timing data, so it can confuse the system and analysis procedure.
• Noise can be introduced based on the hardware & the signal being determined.
• Some logic analyzers capture large amounts of data, but they have less memory capacity, mainly for high-speed signals or long acquisition times.

Applications

The applications of logic analyzers include the following.

• A logic analyzer is an essential tool that analyzes and captures digital signals, mainly for verifying and debugging digital circuits & systems.
• It captures various signals at the same time, traces relative timings & displays data in different formats.
• A logic analyzer in an embedded system is an essential tool for verifying and debugging. So it captures & displays various digital signals by allowing designers to examine timing relationships, overall system performance & protocol behavior.
• These are important for examining timing relationships, recognizing protocol errors & troubleshooting digital hardware.
• It is a very powerful tool that helps designers to identify & troubleshoot digital circuits at the hardware level.
• Logic analyzers are flexible tools used in a wide range of embedded systems and digital design development.

A logic analyzer is a significant tool for analyzing and debugging digital systems, which is capable of capturing and displaying various digital signals at the same time. These are mainly helpful in protocol analysis, digital circuit design, and the development of embedded systems. In addition, they can also capture timing diagrams, state machine traces, and protocol decodes, which makes them priceless to identify & resolve complex problems. Here is a question for you: What is an alternate name for a logic analyzer?