Virtual Machine Environment (VME) eXtensions for Instrumentation (VXI) bus is used for applications involved in computerized testing and measurement. The VXIbus is considered a good choice when both a high level of performance and a more compact size are desired. For such systems, the VXIbus wins out over personal computer (PC) test systems. This is true in spite of the fact that PC-based systems typically offer advantages in terms of size and pricing when compared to other systems.
VXIbus modules and systems were first introduced in the late 1980s by several different manufacturers. Over the years, production has increased, and there are numerous VXIbus products available today. Among these products are computer controllers and instruments for testing. There are even such VXIbus instruments as filters and digitizers. Combined with adequate software, such modules make it possible to create virtual-instrumentation systems.
The VXIbus is based on the Virtual Machine Environment (VME) bus. The VMEbus is quite popular for industrial computing use. As a 32-bit bus, the VMEbus is capable of transferring data at rates as high as 40 megabytes (MB) per second. The VXIbus took the 32-bit VMEbus and made a range of additions, including precise timing signals, module synchronization, and resource management.
VXIbus offers many benefits, including multi-vendor support and the ability to configure systems that meet very specific needs, using a range of common products. VXIbus also allows for protection from electromagnetic interference, shielded modular instruments, and rugged chassis. VXIbus provides for an optimal electrical environment and supports geographical addressing.
Like most things, VXIbus has some disadvantages as well. To begin with, VXIbus modules tend to be more costly than PC add-in cards. Sometimes, VXIbus systems are harder to integrate than those that are PC-based. Fortunately, however, the VXI Plug and Play Alliance, formed in 1993, worked to deal with many common system issues. The efforts of the alliance resulted in the development of standard interfaces designed to make certain that modules work efficiently together at the required levels.