The PCI eXtensions for Instrumentation (PXI) bus builds on CompactPCI to deliver custom instrumentation and automation systems. The PXI standard defines a modular hardware and software framework for interoperability that allows developers to mix and match PXI chassis, controllers, and modules from different vendors. PXI systems also integrate timing and triggering chores.
The PXI System Alliance (PXISA) promotes and maintains the PXI standard. This includes a hardware specification, a software specification, the Virtual Instrument Software Architecture (VISA) for PXI specification, and a module description. These define an environment where a standard controller can work with compliant modules simply by plugging them into a common PXI chassis. The controller will become aware of the resources in a system when it is turned on.
Recognition and communication are just part of the story. PXI also incorporates a pair of timing links necessary for coordinated module operation. This includes a common 10-MHz clock, a trigger bus, and a star trigger controller. Developers can configure the logical linkages between modules in software. It enables standard front-end software to handle a wide range of PXI modules so users don't have to contend with the underlying details. Building a system is a matter of plugging and configuring modules.