LXI
From Free net encyclopedia
LAN eXtensions for Instrumentation (LXI) is a standard developed by the LXI Consortium, it was officially released in September 2005 by Agilent Technologies and VXI Technology. The LXI Consortium now has over 45 companies [1], whose strategic members are (in alphabetical order) Aeroflex, Agilent Technologies, Keithley Instruments, Measurement Computing (MCC, acquired by National Instruments in year 2005), Pickering Interfaces, Racal Instruments, Rohde & Schwarz and VXI Technology.
The LXI standard defines devices using open-standard LAN (Ethernet) for system interdevice communication. The standard will evolve to take advantage of current and future LAN capabilities. It provides capabilities that go well beyond the capability of legacy test and measurement connectivity solutions. LXI will provide users with solutions that are denser, smaller, faster and cheaper than legacy solutions. LXI's choice of Ethernet is based on it being low cost, fully supported on all computer platforms, peer to peer communications, TCP/IP reliability and it's expected long term secure future roadmap whilst maintaining full backward compatbility with all implementations.
The LXI Standard has three key functional attributes:
- A standardized LAN interface that provides a framework for web based interfacing and programmatic control. The LAN interface can include wireless connectivity as well as physically connected interfaces. The interface supports peer to peer operation as well as master slave operation.
- A trigger facility based on the IEEE 1588 Precision Timing Protocol that enables modules to have a sense of time that allows modules to time stamp actions and initiate triggered events over the LAN interface.
- A physical wired trigger system based on a LVDS electrical interface that allows modules to be connected together by a wired interface
The LXI Consortium expects LXI devices to be used in a wide variety of systems, often including devices that are not by themselves LXI compliant. These devices are likely to include IEEE-488, PXI, VXI and LAN instruments with conversion devices where required.
Trigger events over the LAN can be sent by UDP to minimize the latency that can be experienced with TCP/IP protocols. The wired trigger and IEEE 1588 triggers are designed to address concerns about the latency that is sometimes seen in LAN based systems. The defined wired trigger facility provides a triggered mode of operation that emulates trigger signals based on direct point to point connection between legacy instruments. The IEEE 1588 facility allows triggers to be scheduled or events to be time stamped against a system clock.
LXI Devices include web pages that can be opened with a web browser to view and change various parameters the LXI Device has been set to. LXI devices are programmed using standard IVI drivers.
The LXI Standard defines three functional classes of instrument to meet the requirements of different applications:
- Class C. These devices provide a standardized LAN and web browser interface that is compliant with the LXI Standard.
- Class B. These devices provide a standardized LAN interface and support the IEEE 1588 timing aspects.
- Class A. These devices provide a standardized LAN interface, IEEE 1588 operation and physically wired trigger interface.
The standard does permit the wired trigger facility to be present on Class C devices. These classes do not imply any particular physical size for an LXI Device.
LXI instruments are expected to challenge the formally dominant IEEE-488 Instrumentation Bus (originally launched in the 1970's) and to a lesser extent the VXIbus (launched in 1987). To ensure interoperability and a consistent user experience all LXI Products must go through a strict approval process before being permited to use the LXI Logo. A list of approved LXI products, now numbering over 40 instruments, is available from the LXI Consortium web site. [2]
References:
1) http://www.lxistandard.org/ 2) http://www.lxiconnexion.com/ 3) http://www.agilent.com/find/lxi_backgrounder