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

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