What Is a Logic Analyzer?

A logic analyzer is an instrument that analyzes the logical relationships of a digital system. Logic analyzer is a kind of bus analyzer which belongs to data domain test instruments. It is based on the concept of bus (multi-line), and simultaneously observes and tests the data flow on multiple data lines. Testing and analysis of your digital system is very effective. A logic analyzer is an instrument that uses a clock to collect and display digital signals from test equipment. The main function is to determine timing. Because the logic analyzer does not have many voltage levels like an oscilloscope, it usually only displays two voltages (logic 1 and 0). Therefore, after setting the reference voltage, the logic analyzer judges the measured signal through a comparator, which is higher than the reference. The voltage is High and the reference voltage is Low. A digital waveform is formed between High and Low. ^[1]

For example: a test

The logic analyzer is the same as the oscilloscope. It collects the specified signals and displays them to the developer in a graphical manner. The developer analyzes whether the error occurs according to the protocol based on these graphical signals. Although the graphical display has brought a lot of convenience to developers, manually analyzing a series of signals is not only troublesome but also error-prone.

In this fast-developing society, everything is pursuing high efficiency. Automation and intelligence have become the development direction of protocol analysis. Under the guidance of this idea, the protocol analysis function of various test instruments appeared and developed. Most developers can easily find errors, debug hardware, and speed up development progress through the protocol analysis function of test tools such as logic analyzers, which guarantees high-speed and high-quality completion of projects.

On this issue, the developer of Guangzhou Zhiyuan Electronics Co., Ltd. put forward a completely new answer: protocol analysis is a continuum that makes full use of logic analyzer resources in an application field. Regardless of the sampling frequency, storage space, trigger depth, and other resources of the logic analyzer, resources are limited, and we can only exert its maximum effectiveness by fully combining the relevant components of the protocol.

The function of the logic analyzer is to show it in a form that is easy to observe

Logic analyzers are divided into two categories: Logic State Analyzer (LSA) and Logic Timing Analyzer. The basic structure of these two types of analyzers is similar, the main difference between the display mode and the timing mode.

The logic state analyzer uses the characters 0, 1 or mnemonics to display the detected logic state. The display is intuitive. Error codes can be quickly found from a large number of digits, which is convenient for functional analysis. The logic state analyzer is used to analyze the system in real time, check the

The working process of the logic analyzer is the process of data acquisition, storage, triggering and display.

The first generation of the logic analyzer came out in 1973 with slow test speed, simple function, only basic triggering ability and display mode, and timing analysis and status analysis belong to two types of instruments. The second generation of products uses microcomputer as a mark, The analysis and status analysis are combined into one, which is convenient for the software and hardware analysis of the microcomputer. The main features of the third-generation products are high speed, multi-channel, large storage capacity, and analysis capabilities represented by system performance analysis. The fourth-generation products It is marked by a monolithic logic analyzer and has more complete performance.

After the logic analyzer writes the measured data signal into the memory in digital form, all or part of the data in the memory can be stably displayed on the screen through the control circuit as required. The following display modes are usually available.

As mentioned earlier, most logic analyzers are a combination of two instruments, the first part is a timing analyzer, and the second part is a state analyzer.

Number of channels

Where a logic analyzer is needed, to comprehensively analyze a system, all the signals that should be observed should be introduced into the logic analyzer, so that the number of channels of the logic analyzer should be at least: the word length of the system under test ( Number of data buses) + number of control buses of the system under test + number of clock lines. So for an 8-bit machine system, at least 34 channels are needed. The channel number of mainstream products of several manufacturers is as high as 340 channels, such as Tektronix, etc. The mainstream products on the market are 16-34 channel logic analyzers.

Sufficient timing resolution

Timing sampling rate

The logic analyzer is mainly used to locate the specific waveform data when the system runs wrong, and observe the waveform data to infer the cause of the system error, so as to find out a targeted solution to the error.

There are two main methods for locating error waveform data using a logic analyzer. One is to capture a large amount of data during the operation and then use other methods to find the location of the error point in this data. This method is time-consuming and labor-intensive And subject to the storage capacity of the logic analyzer, the target waveform data may not be captured every time; the other is to start capturing data when specific waveform data arrives by triggering to accurately locate the target waveform data.

Trigger concept first appeared

The logic analyzer structure contains a memory

With the development of large-scale integrated circuits and microcomputers, modern digital systems have been microcomputerized. The introduction of microcomputers, on the one hand, greatly improves the system's capabilities and can complete many complex tasks; on the other hand, traditional detection equipment can no longer effectively detect and analyze digital systems, especially microcomputer systems. This is because the data transmission of the digital system is carried out in a manner of spatially distributing multiple code points, which constitute a certain format of data. The transmitted data stream is a data word with discrete time as an independent variable, rather than a waveform with continuous time as an independent variable. Therefore, important parameters such as signal amplitude in analog signal analysis are not so important in digital signal analysis. The latter focuses on examining signals above or below a certain threshold level and the relative relationship between these digital signals and system time. ^[7]