VXI Backplanes

The specification governing VXIbus – an acronym for VMEbus eXtension for Instrumentation – defines the use of 4 x bus module sizes (fig.1), with the “A” and “B” modules being the same as 3U & 6U VMEbus cards. Although the VXI specification, broadly speaking, follows the VME standards, it includes defined functions on the P2 conneector and a further set of functions on the P3 connector. The most important variation in the two standards arises from the fact that any VXIbus instruments incorporated in a system must be capable of being physically screened against EMC on all sides with a provision for additional chassis screening between instruments.