VITA 65 clarifies VPX interoperability profilesStory
February 11, 2010
VPX?s innate flexibility spawns the need for module and backplane vendors to classify product capabilities in a compatible way to move closer to universal interoperability. And OpenVPX (VITA 65) does just that.
New defense and aerospace embedded computing implementations are rapidly migrating from VMEbus to VPX (VITA 46), and the rate of adoption is rising. VPX offers the systems integrator new levels of architectural and performance potential with an abundance of multi-GHz signaling connectivity in proven 3U and 6U packaging standards. However, VPX’s inherent flexibility highlights the need for vendors of modules and backplanes to classify product capabilities in a common way and move closer to universal interoperability. OpenVPX (VITA 65) clarifies the way that products should be classified, thus ensuring, for example, that modules meeting a declared profile are compatible with a backplane slot supporting that profile, and so on.
But VITA 65 is not intended to succeed or replace VPX. Its purpose is to guide the systems integrator toward a viable, interoperable, single- or multi-vendor VPX-based solution. Of necessity, VITA 65 creates an architectural convention representing a consensus of current practice. This convention cannot be fixed forever and might be superseded by new technology as it is introduced into VPX products. As a result, VITA 65 can continuously evolve at the rate of innovation and technology introduction, and planes – along with pipes and modules – are essential ingredients.
An interoperable system is two or more modules plugged into a backplane providing the interconnect between the modules, plus power supplies and a means of thermal management. Architecturally, a VITA 65 system’s interconnections and intramodule communications are characterized by planes and pipes. Five planes are defined: a control plane, traditionally the role for VMEbus but now supplanted by Ethernet; a data plane for intramodule data transfer; an expansion plane for I/O, other types of data movement, or data storage; a management plane (chassis level); and a utility plane (slot level). The control, data, and expansion planes might currently be combinations of Serial RapidIO, PCI Express, or Ethernet, with much of the detail and options available for all five planes already defined by VITA 46 and its dot specifications.
Pipes and modules
Pipes are groups of differential pairs classified only by the number of pairs per pipe. They would typically be used in an application for Serial RapidIO or PCI Express. The definition of pinout is from the relevant VITA 46 dot specifications. Pipes are classified in VITA 65 by their size, from an Ultra Thin Pipe (UTP) with two differential pairs to an Octal Fat Pipe (OFP) with 64 pairs, plus rules for how a module or backplane will support one, two, or none of them. And, finally, VITA 65 defines four slot and module profiles that include a switch, a bridge, a payload (for example, an SBC), or a peripheral. VITA 65 profiles will be created for slots, backplanes, and module types; the pipes and the protocols they support; plus slot size and cooling methodology. To implement a practical application with specific functional and performance requirements, developers can select modules to meet these requirements: Their VITA 65 profiles will lead to slot profiles which, in addition to the system’s architectural needs, will lead to a compatible backplane profile.
It is anticipated that as the market develops, certain profiles will predominate, certainly for laboratory development systems. However, the nature of the VPX market, which is mainly military and industrial, is such that implementations are very closely matched to specific applications, often to optimize Size, Weight, and Power (SWaP). These markets use much special-to-type I/O; hence, VITA 65 makes no recommendations for use of the user-defined pins. As a participant in the development of the VITA 65 standard, GE Intelligent Platforms offers a number of 3U and 6U VPX payload and switch products that meet its classification criteria. One of these is the DSP230 quad depicted in Figure 1.
Figure 1: DSP230 multiprocessor blade from GE Intelligent Platforms
VITA 65 is intended to be a living, breathing document, expanding with market and technology growth, but also able to accommodate deletions or modifications of existing profiles as their usage or applicability changes. VITA 65 brings clarity to the system builder by assuring interoperability of products offered by a broad vendor base while offering those vendors broad enough scope to sustain product differentiation, encourage innovation, and prevent the stagnation of future technology development.
To learn more, e-mail Duncan at [email protected]