VXIbus

VXIbus is a modular instrumentation bus standard designed for automated test equipment. It extends the VMEbus architecture to provide a scalable, plug-in backplane for instrument modules in a chassis. The standard defines mechanical form factors, electrical interfaces, and a software model that enables a System Controller to coordinate a large number of peripheral modules, enabling synchronized measurements, data acquisition, and control tasks.

Form factors and backplane: The most common VXI modules use 3U and 6U Eurocard sizes, sliding into a common backplane that supplies power and interconnect. A typical VXI system includes a System Controller (SC) that manages configuration, timing, and resource allocation, while the remaining modules function as devices on the VXIbus.

Electrical and timing features: The VXIbus backplane preserves VME-like data and address buses and adds a dedicated trigger and event mechanism for synchronization across modules. It supports multiple data-transfer modes, signaling, and timing schemes to enable coordinated multi-channel operations. The standard also specifies power distribution and environmental requirements for reliable operation of stacked instruments.

Governance and usage: Originating in the 1980s as an extension of VMEbus, VXIbus became a widely used platform for automated test equipment in industries such as aerospace, automotive, and electronics. It has coexisted with other standards such as PXI and LXI, with PXI later gaining prominence for PC-based controllers and compact form factors.

Status: VXIbus remains an established, widely implemented standard in many legacy and mission-critical test systems. While new platforms increasingly favor PXI-based solutions, VXIbus modules and systems continue to be available from manufacturers and are still used in various production environments.