VPX and OpenVPX

The VITA Standards Organization (VSO) is an ANSI-accredited group that defineed and developed the key computer specifications such as the family of VPX standards, which include VITA 46.x, VITA 48.x, and VITA 65.

The VITA 46.0-2007 standard specifies the base mechanical and electrical specifications for VPX. Assuming that you have a basic understanding of VME systems, the look and feel of a VPX system is not all that different. VPX maintains the 3U and 6U standard mechanical form factors that currently exist in VME and cPCI systems. The board interconnects are high speed MultiGIG RT connectors from Tyco. These new high speed connectors allow for the use of high speed serial buses upwards of 10 Gbps and beyond. The actual backplane connection uses either 3 connectors (P0-P2) for a 3U card or 7 connectors (P0-P6) for the 6U card. P0 is reserved for the power and system control signals. P1 has a handful of system control signals and the rest can be used for data bus connections between modules. Any remaining unused pins are considered User I/O and are generally routed to either the Rear Transition Module, as additional flash storage, or backup bus lines. All connectors with the exception of P0 are generally routed in differential pairs.

All power and system control signals are routed through P0 as noted above. The only required control signal is the System Reset (SYSReset). Other connections such as providing a reference clock, JTAG, and the system management Bus must be routed on the backplane but are optional in VPX system implementations. Power is routed through the backplane to the VPX board via 6 separate signals as noted in the table below. Note that the 3U and 6U backplanes are inherently incompatible due to the voltage differences on VS2.

1. Max module power of 276W on 3U and 768W on 6U.

Open VPX was the industry’s attempt to bring order to chaos. Open VPX methodically defines a system of profiles that would fully explain the interactions between the backplane and plug-in modules. The profiles are the physical mapping of resources in the system. This information can then be used to determine compatibility. Before diving into the actual profiles, first we need to introduce some new terminology unique to OPEN VPX.

VPX REDI is defined within VITA 48 and standards for “Ruggedized Enhanced Design Implementation”. This standard applies specifically for VPX systems(VITA 46.0 and 65.0) and defines the mechanical interface between the chassis and the plug-in modules. It expands upon the plug-in module pitch from the 0.8” standard defined in VITA 46.0 and adds both 0.85” and 1.0” pitches. The increased size allowance permits the addition of top and bottom side covers to facilitate ESD protection, conduction cooling, and level 2 maintenance. Level two maintenance refers to military grade products that this field replaceable. This adds additional Electrical Static Discharge (ESD) requirements, includes a full metal jacket around all exposed electrical components. The mechanical plates also simplify conduction cooled chassis design
by maintaining consistency across all modules. The mechanical specifications for the various types of cooling that are available in the VITA 48 dot specs is noted in the table below.

1. As of 10/15/10.