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This article was originally written in the period 1995-2000

A growing multi-vendor alliance is keeping the promise that the VXI instrumentation standard would stand the test of time. Step forward then, plug and play…

The VXIplug&play Systems Alliance is an organisation whose members state that they share a common commitment to open, multi-vendor VXI systems. Common standards and practices beyond the scope of the VXIbus specifications are the stated objective, to be achieved by using both formal and de facto standards to define complete system frameworks.

The goal is to improve ease of use and maintain VXI as an open, multi-vendor architecture at the system level, reducing systems integration and software development times. As such, all VXI hardware that is compatible with VXIbus specifications is applicable to VXIplug&play frameworks and vendors do not need to be members of the organisation for their products to be compatible. End users should be able to obtain all these without needing to read any of the detailed specifications, which are more of relevance to vendors.

Areas that will enhance hardware “plug&play” compatibility beyond the scope of the VXIbus specifications include: consistent approaches for connectors; UUT interfacing and fixturing; instrument protocols for shared memory communications; consistency on the use of optional VXI features, such as backplane triggers, interrupts, sumbus and local bus; and common documentation approaches. In addition, a consistent approach for calibration will be developed to benefit both vendors and end users.

The VXIplug&play specifications have now been widely accepted, significantly simplifying the use of instrument drivers and particularly the software integration of multi-vendor systems for automatic test equipment and instrumentation systems.

System software

The alliance is aiming for interoperability for system software, by promoting standardised system software frameworks. Some elements of a system software framework include operating system, programming language, I/O drivers, instrument drivers and higher level application software tools. Many shared architectural elements already exist ion the market today, representing both an opportunity and a mutual responsibility. Several software packages are in use by thousands of end users, so there must be a commitment to maximise compatibility with the installed base.

Having the desire to encourage further commonality in software architecture, the alliance will look to the future and identify key areas for further standardisation. For example, the alliance views instrument drivers, usable both interactively and programmatically as a mandatory software component for every VXI instrument. With the increased use of key computer standards, such as dynamic link libraries (DLL), dynamic data exchange (DDE) and object linking and embedding (OLE), software packages can coexist in the same system and cooperate in exciting new ways.

Rather than limit software choices, the alliance believes that identifying standard software frameworks will minimise duplicated effort on shared architectural elements. This will improve the quality and ease of use of the shared elements and will give vendors an opportunity to focus on extending the scope of their unique added value elements. The alliance believes that standard frameworks are the key to enabling a variety of software tools from multiple vendors to operate cooperatively in the same system. Just as in the Microsoft Windows environment, where framework standards give a tremendous variety of vendors the ability to produce interoperable software products with unique added value, so standard frameworks in VXI should benefit both the user and vendor communities.

I/O driver software

To achieve broad plug and play capability for multi-vendor system software tools, a unified I/O driver software architecture that accommodates all points of view in the market is required as a foundation. Defining such a standard has been difficult in the past, because all major players had not yet documented their products and/or needs in this area. Over the last two years, several major I/O software suppliers have documented their products, declared them to be “open” and lobbied a variety of groups as to the benefits of recognising their product as “the standard”. Most realise, however, that picking a single product implementation as “the” standard would fragment the market. It would guarantee incompatibility with some portion of the installed base and would jettison the existing software tools and systems based on other implementations.

It would also make the eventual interoperability of higher level multi-vendor software tools impossible. Rather than fragment the market, the Alliance is aiming to unify it. All of the major I/O software suppliers have now clearly documented their needs and stated publicly that their defined application programming interfaces (APIs) are open. So it is finally possible to define a single unifying architecture that can deliver interoperability of all existing APIs. This gives compatibility with the entire installed base of applications and all existing software and tools, laying the foundation for eventually achieving interoperability for higher level multi-vendor software tools such as instrument drivers and development environments.

The VXIplug&play Systems Alliance is jointly defining and implementing an I/O driver architecture that provides a unified foundation for all existing points of view, as well as next generation needs. This architecture is a superset of existing announced implementations and includes features such as interface and platform independence and backward compatibility. In addition, it includes advanced features not found in existing implementations that are required for next generation virtual instrumentation.

The assistance of Tektronix, on behalf of the VXIplug&play Systems Alliance, in providing information for the compilation of this article is gratefully acknowleged.

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