The Evolution of Logic Analyzers: Past and Present
A logic analyzer is an instrument used to simultaneously capture, display, and measure multiple electronic signals in digital circuits. Logic analyzers can show the relationships and timing between many different signals in digital systems and are often capable of analyzing digital communication protocols such as I2C, SPI, and serial. Therefore, logic analyzers are the best tools for debugging digital circuits and digital communication systems.Logic Analyzer Decoding I2C and Serial Data
The Invention of Logic Analyzers
The 1960s witnessed the rise of integrated circuits (ICs), meaning circuits began to shrink. In turn, thousands (eventually millions) of transistors could be packaged into a single chip to perform complex digital logic operations, forming the basis for most microcontrollers, microprocessors, and field-programmable gate arrays (FPGAs) as we know them today.As the number of transistors and pins on these ICs increased, testing and characterizing them became increasingly difficult. Oscilloscopes have existed since the 1930s, and while they are often regarded as the de facto testing instrument for many electrical engineers, it proved very costly to add multiple channels to oscilloscopes.In 1973, HP announced the invention of the first “logic analyzer,” capable of measuring and displaying the logical states of a set of LEDs. The HP 5000A was the first commercially available logic analyzer, but it was limited to two channels. In the following years, commercial logic analyzers began to feature dozens of channels capable of reading and displaying digital logic in parallel.Oscilloscopes remain the perfect tool for analyzing how an analog voltage varies over time between two points, often with up to four channels. Even for digital systems, oscilloscopes are very suitable for examining the analog characteristics of signals, such as rise and fall times, ringing, power consumption, jitter, and propagation delay.On the other hand, if you need a higher number of channels to simultaneously track and correlate multiple digital lines, a logic analyzer is the right tool for the job.
What Makes Logic Analyzers Unique?
1. Recording Multiple Input Channels
A significant advantage of logic analyzers is their ability to record a large number of digital signals simultaneously, typically from 8 to 100 channels. While oscilloscopes can also record digital data, they often cannot match the number of channels and recording duration of logic analyzers due to the memory requirements for storing analog data.
2. Complex Digital Triggering
Similar to oscilloscopes, logic analyzers can be configured to start recording upon triggering events. Triggers can be as simple as a single rising or falling edge on a specific channel or can involve a set of complex conditions, including edges or states across multiple channels.
3. Mixed Signal Functionality
Many modern logic analyzers include some oscilloscope functions, and vice versa. These new tools that can record and analyze both digital and analog waveforms are referred to as mixed signal oscilloscopes. Versatile testing devices make it easier to validate complex circuits and systems.Analyzing Digital and Analog Waveforms
4. Portability
Many standalone logic analyzers include screens that can display captured signal data. However, as personal computers have become more powerful with faster peripheral ports (e.g., USB 3.0), some logic analyzers have opted to forgo screens and rely on computer software for analysis. This saves on device size and cost.
5. Convenience of Data Navigation
6. Fast Digital Measurements
Modern logic analyzers and logic analyzer software contain many advanced features to help users validate signals. This includes measuring various aspects of signals, such as pulse width, frequency and period of periodic signals, and duty cycle.If you want to analyze the transmission data between two systems, a logic analyzer can be a valuable tool for timing analysis. For example, in I2C, the data line (SDA) must hold its expected value for a specific time before the rising edge of the clock line (SCL) (depending on the part). This is known as setup time. For most I2C implementations, SDA must also hold its expected value until the subsequent falling edge of SCL. This is known as hold time.A logic analyzer with a sufficiently fast sampling rate can help accurately measure setup and hold times. This helps ensure that the receiver correctly reads your digital message.
7. Decoding and Searching Transmitted Data
Another unique feature of logic analyzers is their ability to decode signals. Most modern digital communication systems are implemented based on a set of protocols. Logic analyzers or their associated software may contain these protocols (known as protocol analyzers) to help you understand the captured data.Using the recorded data, many logic analyzers will allow you to search the data for specific patterns. For example, in I2C, we can search for the bus address of a device, as this will indicate the start of a transmission. Some logic analyzers allow you to set the search pattern as a trigger condition for starting the recording.
Why Do You Need a Logic Analyzer?
While oscilloscopes can measure digital signals in a manner similar to logic analyzers, they are limited by the number of available channels. Oscilloscopes are the right tool for measuring how the voltage varies or fluctuates over time between two points in a circuit.However, logic analyzers are very useful for testing, debugging, and characterizing digital circuits, offering several advantages over oscilloscopes:
– More channels than oscilloscopes
– Characterizing outputs of digital circuits (e.g., FPGAs)
– Fast measurements and decoding of various digital protocols
– PC-based logic analyzers are compact and portable, making them ideal for field debugging
In recent years, the demand for debugging external parallel buses has decreased significantly due to the increased integration scale of digital circuits and the widespread application of system-on-chip technology, leading to a noticeable decline in the demand for traditional logic analyzers. So what makes Tektronix, as the “guardian of logic analyzers,” continue to provide logic analyzer products for customers? Because you still need them!On June 14, 2023 (Wednesday) from 14:00 to 15:15, let’s delve into its evolution, understanding its unique state capture capabilities (nothing outside the heart), and engineers will also collaborate with mixed signal oscilloscopes. If you want to learn more about the irreplaceable functions of logic analyzers, join us live to hear guests discuss the relationship between instruments and Cheng Zhu’s philosophy. Scan the code to register now!During the live broadcast, you can also ask the guests questions and enter to win oscilloscope prizes!Live Agenda:
1. Outdated or Irreplaceable? Let’s delve into the evolution of logic analyzers
