Are you ready for the swap?

With the ratification of the OpenVPX specification last February, the VME successor VPX now has a complete ecosystem for modular serial switched backplane designs that will hit the ground running from the start with compatible products from more than 30 suppliers. The major advantage for OEMs is the combination of greater performance with SWAP (Size, Weight And Power) technologies. So are you ready for the swap?

For a long time, VME technology has been the major standard in rugged COTS embedded aerospace applications and for good reason: developers have enjoyed unequalled flexibility thanks to VME open architecture and its vast ecosystem. The proven level of reliability and robustness has been a major factor too. But with the massive increase of data to be processed from more and enhanced sensors, radio communication, imaging systems, the bandwidth of VME has become a bottleneck for modern aerospace applications. VPX, the successor to the embedded world's most successful standard for open COTS applications, is eliminating these bottlenecks, while sticking with most of the reliable specifications from VME and only changing what needs to be improved.

OpenVPX: the next level of VPX

The VPX family of technologies is improving the widespread open standards of the VME for 6U and 3U boards and ecosystems in terms of performance as well as electrical and mechanical ruggedisation. And, with the ratification of the OpenVPX specification for multivendor, multimodule, integrated system environments by the VITA Standards Organisation (VSO), VPX is ready to roll with a broad range of new aerospace applications. Since February 2010, the OpenVPX (VITA 65) specification completes the VPX technology triumvirate, which specifies the base electrical and mechanical standards on board level (VPX/VITA 46), enhanced mechanical ruggedisation formats (VPX-REDI/VITA 48) and system level interoperability (OpenVPX/VITA 65). This completion represents the most important advance in open standard COTS computing for aerospace applications since VME was introduced nearly 30 years ago, providing developers and system integrators a new level of performance and interoperability for their specific backplane-based system designs while leaving plenty of room for application-specific augmentation.
 
More bandwidth and over the backplane

One of the most important assets of VPX for demanding aerospace applications is serial switched fabric. Serial differential signal transmission – in comparison to parallel data bus systems, like for example PCI – offers the advantages in regards to higher transaction and aggregate bandwidth, lower link latency, increased scalability, and less consumed routing real estate, enabling smaller systems with lower weight.

Multiprocessor systems, which are required in several airborne situational awareness applications, especially benefit from the high bandwidth offered by VPX. Even if the connection to the dedicated boards is made via a single gen 1 PCIe lane, up to 250 MB/s peak bandwidth is available. But it does not stop here, as VPX currently enables a maximum bandwidth of 6.25 Gbaud per second per differential pair. Using a serial point to point communication scheme this means per slot and line, not shared as with a parallel bus. And since PCI express in regards to software is compatible to PCI, the effort for migrating applications previously based on the parallel PCI bus is minimal, accelerating the time to market for OpenVPX designs.

Higher I/O density

Meanwhile, standard I/O interfaces in aerospace applications are also moving to high-speed signals and more sensors and peripherals require an extremely high capacity for application specific I/O pins to the backplane. In fact, many of today's existing products already exceed VME's 205-pin capacity for user I/O pins. For these applications, 6U VPX holds 268 signals for general purpose I/O including 128 high speed differential pairs. The routing for both the serial data busses like PCI express, SRIO and Ethernet as well as the dedicated I/O signal pairs is defined by the backplane. While OpenVPX defines the general pin-out, it enables the use of not only one but several different serial data busses for the dedicated system as well as for the routing scheme over the backplane: switched star or dual-star networks or a fail-safe full-meshed network for redundant signal transmission are all possible.

Furthermore, with VPX, rear transition modules, which tap on totally new fields of application for compact 3U VPX systems are now possible, which extensively use I/Os via the back side of the systems instead of being limited to the space on the front. In this way peripheral-rich applications with robust, long-term available and fast COTS systems can be carried out with great efficiency. This is also interesting for a lot of switchboard applications in which peripherals are connected from the back and user interfaces are on the front.

VPX: a rugged and fitting concept

On the mechanical side, the VPX standard fulfils the highest requirements in terms of robustness, resistance to mechanical stress, corrosion and resistance to bending or incorrect insertion of boards and even outperforms its predecessor. In system casing VPX is compatible to VME, which simplifies implementation of VPX systems considering that many avionics systems currently in use are aging and need to be replaced and upgraded, since modernisation is ideally achieved by changing only modular components that are based on open standards and compatible with existing systems. Furthermore OpenVPX boards support all PMC and XMC mezzanines, helping OEMs and developers to leverage the advantages of the new standard and still use their dedicated extension modules, which can be regarded as part of the core competencies of aerospace OEMs for a faster time to market.

As the rightful successor to VME, VPX ensures continuity for legacy VME users. By providing support for full VMEbus electrical, software and selected mechanics their investments are well protected. Parallel VPX enables OEMs to leverage the broad spectrum of high speed interconnect technologies to design applications that require more performance and lower size, weight and power combined with higher bandwidth, I/O and connectivity density. With the ratification of the OpenVPX (VITA 65) specification, VPX now fulfils all requirements of modern rugged aerospace applications to become the major standard for high speed avionics communication via backplane for the next several decades.

For aerospace manufacturing OEMs, the only major point to know is that the embedded computing market is consolidating. Therefore, technology isn't the only thing that needs to be taken into account. For long-term availability, the entire economical strength of the company also matters. Therefore, for the leaders in the embedded computing market to best be able to leverage ‘ups and downs' in hundreds of vertical markets, it is clearly advantageous to ‘swap.'

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