VME, VPX and VXI Bus Interfaces and Adapters

VME, VPX and VXI bus interfaces and adapters allow VME, VPX and VXI buses to communicate with other types of computer systems and devices. The VersaModule Eurocard (VME) bus is a popular, 32-bit bus used in many industrial, commercial and military applications. VME extensions for instrumentation (VXI) are an electrical and mechanical standard used mainly with automatic test equipment (ATE). VXI allows equipment from different vendors to work together in a common control and packaging environment. VPX (a.k.a. VITA 46) is an ANSI standard based on the VMEbus with support for switched fabric using a high speed connector. VXI combines VMEbus specifications with features from the general-purpose interface bus (GPIB) to meet the needs of instrumentation applications. Other technologies for VME, VPX and VXI controllers and processors may also be available.

Selecting VME, VPX and VXI bus interfaces and adapters requires an analysis of available technologies. The original VME bus (VMEbus) uses Eurocards, rugged circuit boards that provide a 96-pin plug instead of an edge connector for durability. VME64 is an expanded version of the VMEbus that provides 64-bit data transfers and addressing. VME64 features include asynchronous data transfers, an addressing range between 16 and 40 bits, data path widths between 8 and 64 bits, and a bandwidth of 80 Mbps. VME64 extended (VME64x) is an improved version of the original VMEbus that features a 160-pin connector family, 3.3 V power supply pins, bandwidths up to 160 Mbps, injector/ejector locking handles, and hot swap capability. VME160 transfers data at 160 Mbps. VME320 transfers data at a rate of 320 Mbps. VXI combines VMEbus specifications with features from the general-purpose interface bus (GPIB) to meet the needs of instrumentation applications. VME, VPX and VXI bus interfaces and adapters for VPX applications are also available.

There are several form factors for VME, VPX and VXI bus interfaces and adapters. A computer board's form factor describes its shape and physical layout. It also determines the types of cases that can be used to contain the board, and the type of power supplies that can be used. The original VMEbus specification recognizes two types of cards: 3U and 6U.  3U cards, also known as single height boards, are 100 mm x 160 mm with one 96 pin DIN connector (J1 connector) on the rear that plugs into the backplane. 6U cards, also known as double height boards, are 233 mm x 160 mm with a second 96 pin DIN connector (J2 connector). For VXI systems, cards are lettered from A to D. Size A cards are 100 mm (3U) x 160 mm. Size B cards are 233 mm (6U) x 160 mm. Size C cards are 233 mm (6U) x 340 mm. Size D cards are 360 mm (9U) x 340 mm. VXI cards with a height of 360 mm (9U) and a length of 400 mm are also available.

VME, VPX and VXI bus interfaces and adapters differ in terms of specifications, operating system support, and interfaces to other buses. Specifications include number of ports, transfer rate, random access memory type (RAM), and read-only memory (ROM) type.  Some VME, VPX and VXI bus interfaces and adapters are hot swappable. Others conform to requirements from the U.S. Federal Communications Commission (FCC) or feature CE Marking. Support for both proprietary and open-source operating systems is commonly available. Many VME, VPX and VXI bus interfaces and adapters are used with CANbus, DeviceNet, Ethernet, and small computer system interface (SCSI) products. 

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