Performance, PC configuration Because | Agilent Technologies LXI

Many of these systems are created with VXI- or PXI- based hardware and controlled with either an embedded PC or standalone PC connected through an interface card and cable. LXI solves four key prob- lems developers would typically face under these methods:

•Interface: Rather than an MXI or GPIB interface, LXI uses Ethernet, eliminating the need to install an additional interface card in the PC. In addition, there are no proprietary cables or software.

•PC configuration: Because

a PXI cardcage is an exten- sion of the PC backplane, the whole system must be rebooted every time a card is inserted or removed. With LXI, PCs do not require rebooting when connecting or disconnecting instruments. What’s more, some modular LXI instruments allow for “hot-docking” of cards while the power is on (Figure 1).

•Drivers: When a PXI system reboots, the PC uses an instrument discovery process to identify newly connected devices, which usually requires operators to download and install device drivers. The LXI standard specifies the use of IVI-COM drivers, making it easier to work in a variety of development environments. And some LXI instruments can be programmed directly through Standard Commands for Programmable Instruments (SCPI) when greater func- tionality or performance

is required.

•User interface: With no front panel interface, using PC-based system software to diagnose problems in PXI and VXI devices can be difficult. With benchtop LXI instruments, the front panel interface makes it easy for developers to experiment with an instrument. While most modular LXI instruments lack a front panel, their built-in Web interface makes it possible to learn the capa- bilities by simply opening a Web browser on the connected PC. The browser function also makes it easier to see what’s happening with the equipment, simplifying system support and ensuring greater uptime.

2. Performance

Automotive electronics test- ing includes everything from complex power train control modules requiring hundreds of tests, to simple airbag squib modules, to telematic/infotain- ment modules that may involve time-consuming transfers of huge data files. These tests often challenge GPIB’s maxi- mum data rate of roughly

1 MB/s. With LAN, I/O transfer speed is becoming a non-issue with 1-Gbit/s connections becoming commonplace and 10-Gbit/s on the way.2

I/O performance should not be an issue for LXI devices in typical automotive applications that require both transactional programming and transfers of large data blocks such as wave- forms captured by digitizers. In transactional programming, there is a well-understood issue around LAN latency. Instrumentation vendors are reducing the number of required communication cycles by preloading instructions to LXI devices.