A look into the history of the mixed-signal oscilloscope
1996 was a year to remember, it brought us the Macarena, the Nintendo 64, and the first Motorola flip phone. But, also making its debut that year was the HP54645A mixed signal oscilloscope. Today mixed signal oscilloscopes (MSOs) are an industry standard, but this was new and exciting technology 20 years ago. Here’s an excerpt from the HP journal from April 1997:
“This entirely new product category combines elements of oscilloscopes and logic analyzers, but unlike previous combination products, these are “oscilloscope first” and logic analysis is the add-on.”
At this point in the tech industry, microcontrollers dominated the landscape. Gone were the 1980s and the days of microprocessors and their dozens of parallel signal lines, in was the 8-bit or 16-bit microcontroller. As the need to test dozens (or hundreds) of channels decreased, the thriving logic analyzer industry began to shift in favor of oscilloscopes. As a result, Hewlett Packard released the 54620A; a 16-channel timing-only logic analyzer built into a 54645A oscilloscope frame. This was a big hit for engineers who only needed simple timing analysis from a logic analyzer and liked the simplicity and responsiveness of oscilloscopes.
These tools were all coming out of Hewlett Packard’s famed “Colorado Springs” division, which focused heavily on logic and protocol products. In hindsight it’s clear that the shift from a logic analyzer-focused landscape to an oscilloscope-focused landscape was inevitable. But, when the project funding decisions had to be made the logic analyzer was king.
A few R&D engineers, however, saw it coming. They strategized amongst themselves to get a new oscilloscope project underway. However, they knew it was going to be a hard fought battle. Following the old adage “if you can’t beat them, join them,” the engineers proposed a new project combining the oscilloscope and the logic analyzer into one frame. The thought was that if an oscilloscope project wouldn’t get funding, then surely integrating a logic analyzer into the scope would do the trick. Below is a picture of Bob Witte’s (RW) original notes from the 1993 meeting in which the MSO was conceived. (Follow Bob Witte on Twitter: @BobWEngr) This product was internally code named the “Logic Badger,” stemming from the 54620A oscilloscope’s “Badger” code name and the 54645A’s “Logic Bud” code name.
One thing led to another, and the 54620A and the 54645A were combined into the paradigm shifting 54645D. A new class of instrument was introduced into the world: the mixed signal oscilloscope. For the first time ever, engineers could view their system’s timing logic and a signal’s parametric characteristics in a single acquisition using the two analog oscilloscope channels and eight logic channels.
From its somewhat humble beginnings, the MSO has become an industry standard tool globally, with some estimating that up to 30% of new oscilloscopes worldwide are MSOs. Logic analyzers are also still sold today and are an invaluable tool for electrical engineers thanks to their advanced triggering capabilities, deep protocol analysis engines, and state mode analysis. If you’re debugging FPGAs, DDR memory systems, or other high-channel-count projects you’ll want to consider using a logic analyzer. However, mixed signal oscilloscopes dominate today’s bench for their ability to quickly and easily trigger and decode serial protocols.
Finally, it’s worth noting that the Hewlett Packard division is still alive and strong in its current form here at Keysight Colorado Springs. In fact, many of the same engineers from the very first MSO project are still here working on today’s (and tomorrow’s) MSOs.
To learn more about how the digital channels on an oscilloscope work, check out this 2-Minute Guru videoon the Keysight Oscilloscopes YouTube channel.