GETTING THE MOST OUT OF YOUR
MIXED SIGNAL OSCILLOSCOPE
Measurement trips and tricks for getting the most out of your MSOs
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mixed signal oscilloscope (MSO) is a 2- or 4-channel oscilloscope with 8 or 16 (rarely more) logic analysis channels built in for timing analysis. The main benefits of this integration are time correlation between signals on the analog and digital channels of the oscilloscope and more powerful triggering between the two.
MSOs — a brief history If the 1980s were the decade of the microprocessor, the 1990s were the decade of the microcontroller. Miniaturisation and digitisation of electronics was happening, and happening fast. Classically, a design engineer had two key tools on their bench: an oscilloscope and a logic analyser. These were purpose-built tools with amazing performance and capabilities. Oscilloscopes were unmatched in showing signal quality and integrity at the physical layer, with high resolution and fast waveform update rate. Logic analysers traditionally had 64 or more digital lanes with ultradeep memory, timing analysis, state analysis and full customisation of the user interface. They were useful for debugging and designing even the most complex FPGAs, ASICs and
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microprocessors. But the needs of engineers were changing, and with that, the tools changed too. Microcontrollers of the time were usually 8- or 16-bit devices, and the swing from parallel to serial communications was already happening. Logic analysers were a tool of last resort — often way overpowered for the task at hand. People who weren’t power users often struggled to set up and use the device. Engineers needed an easy-to-use and portable logic analyser with a familiar interface. The solution was the Hewlett Packard 54620A, a 16-channel timing-only logic analyser in a 54645A oscilloscope’s housing, with an oscilloscope user interface. This product was successful with engineers who needed simple timing analysis, without the other 95% of capabilities in comparatively complex and expensive logic analysers.
Target applications Engineers were, for the first time ever, able to make analog and digital acquisitions simultaneously with fast update rate. This was, and still is, important for designers who are conscious of transients and physical layer phenomena in digital design. Let’s take a look at some popular applications for mixed signal oscilloscopes today.
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