VME

VME, short for Versa Module Europa, is a computer bus standard for modular backplane-based systems built around Eurocard cards. Developed in the early 1980s by Motorola, it was designed to be an open, scalable, and robust solution for embedded and industrial computing. Over time it became widely adopted in sectors such as manufacturing, aerospace, defense, and scientific instrumentation. The standard has evolved through revisions such as VME64 and VME64x, and is maintained by the VMEbus International Trade Association (VITA) as part of a family of related specifications.

Architecture and features: VME uses a backplane that hosts multiple plug-in cards (typically 3U or 6U Eurocards) and provides a parallel data bus along with address and control lines. The design supports multiple bus masters, meaning devices can initiate data transfers, and includes mechanisms for arbitration, interrupts, and direct memory access. The original implementation commonly used a 32-bit data path with address widths varying by variant, and operation depends on the backplane and cards installed. VME cards connect to the backplane via standard connectors and signaling schemes, with later revisions introducing broader capabilities.

Variants and evolution: VME64 introduced wider address and data possibilities, enabling larger address spaces and, in some configurations, 64-bit data paths. VME64x refined connectors and added features to improve performance and flexibility while preserving compatibility with earlier VME and VME64 equipment. Across its generations, VME maintains backward compatibility so older cards can operate in newer backplanes where supported.

Applications and status: VME remains common in legacy industrial control, test and measurement, avionics, and research environments due to its robustness, long product lifecycles, and mature ecosystem. In newer systems, it is often complemented or replaced by modern standards such as VPX or PCIe-based architectures, though many installations continue to rely on VME for critical workloads.