Hybrid backplane
OpenVPX
The OpenVPX standard from VITA refines existing standards to provide a more streamlined approach to high-speed 3U and 6U VPX (VITA 46) board-based system design. The original set of VPX specifications offered a plethora of options, many of which were rarely used. On the other hand, several configurations were commonly employed, but designers lacked standard choices prior to OpenVPX.
Unlike individual standards such as those under VITA 46, OpenVPX (VITA 65) defines system topologies based on these other standards, limiting the selections and providing a coherent definition system for everything from backplanes to the types of high-speed pipes employed in the design.
OpenVPX has achieved wide support and fast adoption by a rather large group of VPX supporters. It’s being utilized in designs and system definitions as many companies transition from VME to VPX. For example, Elma has hybrid backplanes that support VME and OpenVPX (Fig. 1).
OpenVPX Supports Variety
The OpenVPX specification defines standard profiles for the chassis, backplane, slot, and module (see “OpenVPX Accelerates Military Time-To-Market”). Chassis profiles define mechanical specifications such as the number of slots. Backplane profiles specify how slot profiles are interconnected. Slot profiles define the planes including connection type, size, and number of pins as well as user-defined pins.
The utility plane is common to all slots. The maintenance plane addresses module monitoring and chassis status. The control and data planes address typical system configuration needs. The module definitions define how these planes are implemented while also addressing power and cooling.
Standard high-speed serial connections address existing standards like Ethernet, PCI Express, and Serial Rapid IO. The pipe designation matches the lane specifications for these high-speed serial interfaces starting with x1 configurations and increasing with higher-bandwidth, multilane pipes.
OpenVPX still allows a wide variety of backplanes and module implementations like single-board computers from GE Intelligent Platforms, Curtiss-Wright Controls Embedded Computing, and Mercury Computer Systems (Fig. 2).
The General Electric SBC612 brings octal core Freescale P4080 processors to the mix with PMC/XMC sites and Gigabit Ethernet and Serial Rapid IO connectivity. Curtiss-Wright’s Champ-AV6 uses multiple Power-based microcontrollers, while Mercury Computer brings Intel-based solutions to the mix with its Ensemble 6000 SBC6521.
Custom backplanes will still make up a significant chunk of hardware in the military and aerospace arenas, but OpenVPX makes commercial off-the-shelf (COTS) more practical. OpenVPX also makes a better starting point, even when designs deviate to custom configurations.