VXS System Platforms, Backplanes, and Accessories

ANSI/VITA 41, VMEbus Switched Serial or VXS, is an ANSI standard that combines parallel VMEbus with enhancements to support switch serial fabrics including PCI Express, Rapid I/O, StarFabric and Infiniband over a new high-speed PO connector.

Backward compatibility is maintained with existing backplanes that do not have a conflicting P0 scheme.  Combining the VME2eSST parallel bus with switch fabric technologies for multi-point, high-speed data transfers creates choices for embedded computing designs of all types.  The standard also incorporated ANSI/VITA 1.7, allowing more DC power input to each board.

VXS Overview

The VXS Switched Serial (VXS) standard comprises this base standard defining physical features of VXS components, coupled with a set of protocol layer standards to define the specific serial interconnect used in a system implementation. 

The VXS base standard defines physical features that enable high-speed communication in a VME compatible standard.  These features include:  addition of a high-speed connector to the VME64x board in the P0/J0 position, a 6U by 160mm by 6HP (1.2") Eurocard format with many high-speed connectors which may act as a switch, and the backplane/chassis infrastructure needed to support these features.

The ANSI/VITA 1.1, VME64 Extensions standard defines the use of a high-density connector (MultiGig RT 2) in the P0/J0 position. Alternate connectors are permitted but no keying mechanism is required to keep dissimilar connectors from being damaged. In addition to defining a high-speed connector in the P0/J0 area, VXS also defines alignment and keying features which may be used to protect this and future alternate connectors.

The ratio of one high-speed connector per payload board to many on the switch card lends itself to a star topology where each payload card is connected to a central switch. For higher reliability and/or load balancing, two switch cards may be used in a dual star configuration. Interswitch links may be included for reliability and load balancing reasons as well. Although this topology is not required it is a natural fit for the system features.

Standard VME boards may be installed in the VXS payload slots but they will not participate in the high-speed communication. Multiple high-speed serial links interconnect the switch slots.

Protocol layer documents builds upon the VXS base standard by describing how VXS boards may communicate in a standard way using the various switched fabric  protocols such as Ethernet, PCI Express, Serial RapidIO, Infiniband, and Aurora. Pinouts for both the payload and switch boards are given, as well as the value of the VXS key which indicates the protocol.

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