Implementing the VISA specification
This document discusses the VXI Plug and Play Alliance VISA specification and its implementation for Test & Measurement equipment, and outlines the essential elements of such an implementation.
This Virtual Instrument System Architecture (VISA) specification defined by the VXI Plug-n-Play Alliance is an important step in the direction of plug and play interoperability between test and measurement software, instruments and controllers. The VISA framework standardizes the I/O layer between instrument drivers and controllers and supports GPIB, GPIB-VXI, VXI, MXI, Ethernet TCP/IP and Serial bus controllers and interfaces.
The VISA specification, currently at version 2.2, is a moderately complex spec from an implementation point of view. The specification documentation is quite good and covers some recent additions brought forth due to earlier ambiguities. The specification describes an abstraction layer and a set of interface functions, as found in most layered architectures (e.g. the TCP/IP stack).
