VPX Moves Forward With OpenVPX And Additional VITA Specs

June 1, 2010
John Wranovics discusses the ins and out of the latest VITA 66 and 67 standards.

While the venerable VME bus remains strong in legacy deployed systems, newer rugged deployed aerospace and defense platforms are turning to the new VPX (VITA 46/48) and OpenVPX (VITA 65) standards. Helping to speed the acceptance of VPX are complementary VITA standards, including VITA 42, VITA 57, VITA 66, and VITA 67.

One example of a VPX-based military system is a radar processing subsystem that Curtiss-Wright provides to Northrop Grumman in Baltimore, Md., for use in the U.S. Marine Corps Ground/Air Task Oriented Radar (G/ATOR) program.

Mounted on a high-mobility multipurpose wheeled vehicle (HMMWV), G/ATOR uses active electronically scanned array technology to provide aircraft detection and tracking, cruise-missile detection and tracking, ground-weapon location, and air-traffic control. Its modular architecture is designed to deliver operational flexibility and the ability to incorporate new processing platforms and technologies as they become available. The rugged, air-flow-through, radar processing subsystem VPX-based architecture provides a modular, scalable solution.

For aerospace and defense deployed systems, the three VPX technology standards—VITA 46, VITA 48, and VITA 65—are defining the future of military embedded computing. VITA 46 defines the electrical aspects of VPX, while VITA 48 defines the mechanical aspects. VITA 65/OpenVPX defines how an integrator can use VPX to build systems. Together, these specifications are rapidly becoming the industry standard for new programs going forward, thanks to their increased I/O capability and their ability to handle higher density cards.

Helping to take VPX further are complementary VITA specifications such as VITA 66, which defines the use of fiber-optic connectivity out the backplane, and VITA 67, which defines the use of coaxial RF out the backplane. Both of these standards will bring new capabilities directly onto the backplane and therefore directly onto new boards once those standards are finalized.

The VITA 42 (XMC) module standard is well established now. With its support for PCI Express, it has built on the popularity of the legacy PCI-based PMC mezzanine standard. Not as well known as XMC is the VITA 57 (FPGA Mezzanine Card, or FMC) standard. FMC was designed to provide a method for getting high-bandwidth, low-latency signaling directly into FPGAs.

The approach FMC offers is elegant and straightforward. It uses no protocol. Instead, it provides low-voltage differential signaling (LVDS) directly to the FPGA, enabling higher bandwidth than an XMC card would be able to provide from the mezzanine down to the basecard.

In addition, the FMC is about a third the size of the XMC. FMC cards also are designed to do I/O matching. So whether the application requires analog-to-digital converstion or digital-to-analog conversion, or a CameraLink or Serial FPDP (SFPDP) interface, there is a cost-effective, compact FMC card ideal for the task.

While several other types of I/O interfaces are available, they don’t get LVDS directly to the FPGA. They aren’t general purpose. And, they don’t work with other cards. They only work with FPGA cards. FMC cards, on the other hand, address a broad level of applications.

For example, we see a lot of demand for FMCs in signal intelligence applications, and even in some radar applications, where IF-type frequencies come into the basecard and analog-to-digital operations are being applied directly to baseband, after which the data is sent to the FPGA for preprocessing. FMCs are ideal for any application where an analog signal is brought into the system, not just signal processing applications.

FMCs can be used with mission computers or other types of computers where I/O is brought in to perform some kind of FPGA processing, for instance. They’re tied directly to an FPGA. So if you need to do anything with an FPGA, whether it’s data conversion or a kind of image processing or signal processing in the FPGA, like beamforming algorithms, and you need to bring the signal directly into the FPGA, FMC provides a superior way with significant advantages over an XMC module or a “backlink.”

On the other hand, FMC today is front-panel only. No provision exists yet to provide the same capability out the rear to the backplane. Today, FMC is mostly seen in convection-cooled applications. If the platform uses conduction cooling, you typically have to use front-panel I/O.

Going forward, an area of great interest to us and to our customers is VITA 66, which defines the use of fiber-optic connectivity out the backplane, and VITA 67, which defines the use of coaxial RF out the backplane. Both of these standards will bring new capabilities directly onto the backplane and therefore directly onto new boards once those standards are finalized.

VITA 66, the fiber-optic specification, promises to benefit many military applications. In many systems, if there is, for example, a 10-Gigabit Ethernet port out the chassis, fiber-optic connectivity will be used. But today, fiber optics requires front-panel I/O.

In general, fiber-optic and RF connections aren’t dataplane data-transfer mechanisms in the chassis. Instead, they require external data to be brought into the chassis onto your basecard. While it is possible to bring fiber optics or RF in via the front-panel today, it requires the use of a proprietary technique to route the fiber optics to the rear of the card, snaking the fiber-optic cable around, because you still have to bring the data off the card via the front-panel.

VITA 66 and VITA 67 enable fiber-optic or RF connections to replace VPX connectors on the backplane, with blindmate connectors, so RF and optical data can be brought directly into the backplane and then directly into the back of the chassis. This preserves the ability to provide two-level maintenance because you no longer have to disconnect fiber-optic or RF connectors off the front of the card. This makes the job easier for the system integrator because all of the connections are out the rear of the chassis.

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