VME eXtensions for Instrumentation

The VME eXtension for Instrumentation Bus ( VXIbus ) is a common in industrial metrology bus system. The VXIbus is an extension of the well known in the industry VME bus, the VME bus was originally developed specifically for use with the 68000 series of processors from Motorola. Operational areas of the VXIbus are for example in the range automatic test systems in electronics manufacturing.


1985 presented Hewlett -Packard, Tektronix, Wavetek, Racal - Dana and Colorado Data first developed for the U.S. military VXIbus. Since 1987, the company- wide standardization and further development within the VXIbus Consortium is driven and is defined in the IEEE Standard 1155-1992. The VXIbus Consortium members include the company Agilent, Bustec, Tektronix, Wavetek, Fluke and National Instruments.


In contrast to the VME bus of the VXI bus has a dynamic addressing, manual address and Interruptvergaben. To prevent malfunctions due to duplicate addresses. In this context, a similar trend has been observed in the PC sector when changing from ISA to PCI bus, the VXI bus was standardized before the PCI bus. The VXI bus has, among others, the following performance data:

  • A 32-bit address bus
  • A data transfer clock of up to 16 MHz
  • The ability to address up to 256 devices to a single bus
  • A multi- master capability, allowing multiple "master " devices can be operated on one bus simultaneously

Applications are in industrial test systems, the VXI bus is also used for the operation of real-time applications.

The VXI bus competes with the GPIB bus, as so-called GPIB bus -enabled " stand-alone " devices such as oscilloscopes, function generators, programmable power supplies and digital multimeters are realized more often in the form of VXI bus modules. In addition to extensions and improvements within the electric signal diversity and the range was extended to the available module sizes, VME modules can be operated using appropriate adapters in VXI mainframes. The addition of the "Size C" - and "Size D " modules makes it possible to accommodate complex instruments in one slot.

The most common size is "Size C". The module width was widened for VXI devices to 1.2 inches, so that the use of shielded enclosures and housing internal shielding surfaces is facilitated. This reduces the risk of electric shock and sensitive measurement technique is better protected in the shielded VXI enclosures against external interference.