Magic Bus: What Makes Modular Backplanes So Special?

While The Who sang about a bus in 1968 that transports people, digital designers use the same term for an electrical path that transports data.  In modular instrument systems, buses can also transport timing and even analog signals.  In today’s post, I’ll summarize the topologies that make up a modern instrumentation bus, whether VXI, PXI or AXIe.  These topologies are critical to modular instruments and are the basics that enable many of the unique features that modular instrumentation brings to the marketplace.

A modular backplane is not a single bus, but several buses, each bringing different functionality. The geometric pattern of each bus is called its topology. There are three common bus topologies in a modular standard: parallel, star and local. Each brings their unique aspects to whichever standard they support. Understanding these allows users and vendors to understand the tradeoffs made within each standard.

To read my explanation of each bus topology, go here.

By Larry DJ

AXIe: Time for us to watch “Big Brother”

AXIe is often referred to as the “big brother” of PXI.  It is a large format modular instrument standard with many similarities to PXI.  A quick summary of the AXIe standard and its applications can be found here.  You can see why AXIe is called PXI’s big brother. The photograph of the two modules together shows the module size of AXIe is deeper, taller, and wider than PXI.

As we approach the two-year anniversary of the first AXIe specifications, I thought I might give an overview of where AXIe stands in the industry. AXIe is finding applications in Mil/Aero, semiconductor, and physics.  In this week’s blog I summarize what is driving adoption in each segment and offer observations of where AXIe sits as a standard. You can find the my blog here.

By Larry DJ

PCI Express – Eat Your Serial

In a previous blog post PCI Express – Espresso for Test Systems, I explained why adopting PCIe was like your test system downing a dozen espresso shots.  The speed gains are truly impressive.  I focused on the interactive speed of PCIe when coupled with C-based drivers and register-based programming.  50:1 speed improvement is well documented.  Both PXI and AXIe are based on PCIe.

But PCIe also brings the Basic Four of speed: raw speed, scalable speed, parallel speed, and future speed.  Find out why PCIe enables these four amazing speed aspects here.

By Larry DJ

Star Trek, The Next Generation…Instrument Standard

My recent blog post [RF] Space, The Final Frontier attracted several comments from readers, all in the same Star Trek meme.  Well done! But in this post I answer one particular reader’s question, “What comes after PXI, and how long does this federation last?”

This is tough to predict, but I give one option- a standard that focuses on cost, ease of use, and bench applications while maintaining backwards compatibility with PXI and AXIe. How is this possible? Keeping with the Star Trek theme, I call it StarX, an abbreviation of Star Trek Extensions for Instrumentation, The Next Generation. StarX’s continuing mission is to explore strange new form factors, seek out new interfaces and new drivers, and to boldly go where no standard has gone before.

Read about StarX here.

By Larry DJ