VMEbus

VMEbus (Versa Module Europa or Versa Module Eurocard bus) is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. It is physically based on Eurocard sizes, mechanicals and connectors (DIN 41612), but uses its own signalling system, which Eurocard does not define. It was first developed in 1981 and continues to see widespread use today. In 1979, during development of the Motorola 68000 CPU, one of their engineers, Jack Kister, decided to set about creating a standardized bus system for 68000-based systems. The Motorola team brainstormed for days to select the name VERSAbus. VERSAbus cards were large, 370 by 230 mm (14 1⁄2 by 9 1⁄4 in), and used edge connectors. Only a few products adopted it, including the IBM System 9000 instrument controller and the Automatix robot and machine vision systems. Kister was later joined by John Black, who refined the specifications and created the VERSAmodule product concept. A young engineer working for Black, Julie Keahey designed the first VERSAmodule card, the VERSAbus Adaptor Module, used to run existing cards on the new VERSAbus. Sven Rau and Max Loesel of Motorola-Europe added a mechanical specification to the system, basing it on the Eurocard standard that was then late in the standardization process. The result was first known as VERSAbus-E but was later renamed to VMEbus, for VERSAmodule Eurocard bus (although some refer to it as Versa Module Europa). At this point, a number of other companies involved in the 68000's ecosystem agreed to use the standard, including Signetics, Philips, Thomson, and Mostek. Soon it was officially standardized by the IEC as the IEC 821 VMEbus and by ANSI and IEEE as ANSI/IEEE 1014-1987. The original standard was a 16-bit bus, designed to fit within the existing Eurocard DIN connectors. However, there have been several updates to the system to allow wider bus widths. The current VME64 includes a full 64-bit bus in 6U-sized cards and 32-bit in 3U cards. The VME64 protocol has a typical performance of 40 MB/s. Other associated standards have added hot-swapping (plug-and-play) in VME64x, smaller 'IP' cards that plug into a single VMEbus card, and various interconnect standards for linking VME systems together. In the late 1990s, synchronous protocols proved to be favourable. The research project was called VME320. The VITA Standards Organization called for a new standard for unmodified VME32/64 backplanes. The new 2eSST protocol was approved in ANSI/VITA 1.5 in 1999.