VITA 74 VNX

The VITA 74 Small Form Factor standard defines both mechanical and electrical standards to implement a small form factor system. The standard addresses a need for a common approach to small-scale systems to be used in a range of applications. The standard encourages multiple vendors to supply components to be used in small systems at various levels, including modules, backplanes, enclosures and completed solutions. The goal is to allow vendor implementation flexibility at the same time as ensuring component interoperability.

In order to take advantage of previous work, the VPX standard was used as a basis for VNX. The VNX standard takes many of the conventions and leverages the signal definitions into a small form factor environment. The standard adopts the signal mappings, introducing a new high-speed low-cost connector and reduces the number of serial fabric options. The result is a standard that has two serial fabrics, Ethernet and PCI Express. In the interest of keeping the system as simple to implement as possible, a single CPU root node is specified.

The base standard gives details on the mechanical implementation of the system plug-in modules. Two types are defined, 19mm and 12.5mm. Each type addresses a different set of functions. Fabrication of the module enclosure is left to the vendor. In addition, details are provided for the module base carrier board, including connector location, assembly hole locations and component keep-out. The 19mm module has room for a two-board stack. The inter-board connector selection is outside the scope of this standard.

Finally, even though the standard doesn’t specify backplane implementation, details are provided as part of a 4-slot backplane. This can be used as a design starting point for doing a derivative implementation, as defined by the particular application. Also, an example chassis with detail dimensions is given as a starting point for a chassis design. The chassis example can be reproduced in whole or modified a required depending on the requirements.

VNX was expanded to VNX+ under VITA 90.x standards to improve the performance capability of the VNX technology.

Introduction

The tactical payload embedded marketplace operates with unique requirements that drive SWaP (Size, Weight, and Power) to the extreme. Like the commercial counterpart, there are still requirements for high performance but at a much-reduced size and power. VITA 74 standard based products serve markets needing ruggedized products requiring Data Plane interconnect technologies that closely follow the industry state of the art. Switched serial technologies are available that provide significant benefits and scale over the long term. The benefits of these technologies are widely known with many products currently in the market incorporating one or more of these.

This document provides a standard mechanical format for standardization of switched serial interconnects for Small Form Factor applications, with specific concern taken to allow deployment in ruggedized environments. There are many candidate technologies for switched serial interconnects. These include without limitation: Gigabit Ethernet and PCI Express. There is also the need for legacy I/O interfaces that provide connection to standard serial, graphics and USB devices.

The usage model for the Plug-In Modules described in this standard is very different than other Plug-In Modules in the VITA family of standards. Plug-In Modules are installed into an open frame backplane and then the chassis walls are attached, as opposed to a typical VPX or VME implementation where Plug-In Modules are installed into a fixed wall chassis.

Objectives

The objectives of this standard are:

• Define a 12.5mm and 19mm family of Small Form Factor Plug-In Modules
• Define a suitable high-speed connector family for use in Plug-In Modules
• Make provision for switched serial interconnects between Plug-In Modules
• Accommodate Open Standard technology for switched serial interconnects
• Make provision for additional I/O capability at the Plug-In Module level
• Define a mechanical standard for the Plug-In Modules
• Define an optional provision for two-level maintenance Line Replaceable Modules

Overview

The VITA 74 family of standards consists of this base standard, which defines physical features of compliant components; protocol layer standards, which define specific serial or parallel interconnects used in a system implementation.

ANSI/VITA 74.0-2017 allocated multiple dot standards which have migrated to VITA 90.x VNX+. Hence, they are no longer needed. P

The VITA 74.0 base standard includes features drawn from [IEEE 1101.2-1992] (conduction cooled Plug-In Modules). These features are evident in the mechanical drawings provided.

The VITA 74 base standard defines physical and electrical features on the VITA 74 Compliant System Plug-In Module that enable high-speed communication in a compliant system. See Figure 1.2‑1 through Figure 1.2‑4. These features include a definition of two module sizes; a 78mm x 89mm x 19mm module and a 78mm x 89mm x 12.5mm module, both with high-speed differential and single ended signals. The electrical signal definitions, differential, single-ended, power and maintenance are defined in the base standard as interconnects. The base standard includes a standard fabric type, PCI-Express. The PCI-Express fabric acts as the main conduit for I/O internal to a system.

The base standard also defines alignment and polarization features used to protect the connector system. The Plug-In Modules can only be oriented in one direction when being inserted into a slot. This polarization is implemented in the module mechanical shell, its associated slot guide, the connector and its counterpart on the backplane.