PXI vendor looks for synergy with LXI
By Rick Nelson, Chief Editor -- Test & Measurement World, 2/1/2005
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| David Owen expects PXI instruments (top) to coexist with LXI instruments, which he says represent an evolutionary path for his firm’s established IEEE 488 instruments (bottom). |
Owen noted that LXI will support peer-to-peer operation in the same way that IEEE 488, or GPIB, is able to. With LXI, he said, "An instrument can be a controller if, for example, it needs to dump a graphical result to a printer or needs to manage other types of peripherals. In PXI, of course, the controller alone would do this function."
| PCI vs LXI at a glanceRead other articles from this PXI Test Report: Editor's note PXI marches on PXI vendor looks for synergy with LXI PXI Web sites worth a visit |
Owen explained that LXI will optionally include a trigger function based on the IEEE 1588 Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems, a feature that standard instrument LAN interfaces do not support.
"The support of IEEE 1588 will enable LXI to duplicate the trigger features on IEEE 488 systems," he said. "In some ways, this mirrors the evolution of GPIB.
"Early implementations, particularly when it was known as HPIB, had a common set of physical principles, but instruments tended to behave very differently and make different demands on the programmer, requiring the user to be aware of the differences. LXI needs to make the principles and software common in the same way as GPIB was forced to."
He contrasted LXI and PXI instruments, saying, "LXI instruments will have their own power supplies, cooling systems, and LAN controller interfaces with a mechanical form factor that is typically larger than a single PXI module. So, LXI instruments are likely to have more complex functionality and a more controlled environment, with respect to screening and isolation, for example. You would therefore expect that more complex instruments with higher performance levels could be easier to implement in LXI.
"I expect LXI to be able to host bulky high-power instrumentation and switching. The Web-based front panel of LXI will be particularly useful for remote operation, in this case 'remote' potentially being a very long distance indeed."
As for PXI, Owen said, "The smaller module size of PXI permits systems to combine a diverse array of different types of products into a compact form factor. In some cases, such as DMMs and switching, the performance and functionality of these modules challenges or exceeds the capability of bench instruments. In other cases, the performance is more limited, such as RF signal generation and analysis.
"The limitations arise because of the small footprint, the presence of the PCI backplane, and the potential interaction of modules performing other functions. For functional test, where the majority of PXI applications are focused, these issues are of little relevance, so PXI will remain an ideal platform for adding these diverse functions to an ATE system."
PXI systems already co-exist with bench instruments in ATE systems because of product availability and performance issues, Owen said, and he noted that in many cases the bench instruments could be replaced with an LXI-based solution.
"Clearly," he said, "there will be direct competition between LXI and PXI in some areas, but that always happens when new platforms are introduced. PXI is a growing sector, though, and LXI is as likely to increase PXI business as to decrease it.
"We think LXI is more likely to be a challenge to bench instruments and VXI in manufacturing test than to PXI. These products have addressed more complex instruments, not too dissimilar to those where LXI will have a strong presence in a few years time."
In conclusion, Owen said, "The LXI environment will be well-suited to the development of instrumentation with the highest parametric performance. We expect PXI systems and LXI-based instruments will coexist in many test systems, serving the functions that each is best suited to."
| Feature | PXI | LXI |
| Architectural overview | CompactPCI bus with extensions for instrumentation. | Ethernet local-area network with extensions for instrumentation. |
| Heritage | ISA and PCI personal-computer buses. | RS-232 serial bus, IEEE 488 parallel bus, and Ethernet. |
| Controller | Dedicated controller per rack performs control operations. | Each instrument may serve as controller. |
| Advantages | Potential for one compact system to combine a diverse array of instrumentation functionality. | Potential for high parametric performance and well-controlled environment with respect to factors such as EMI/RFI isolation. |
| Specification status | Hardware revision 2.2 released September 22, 2004, and software revision 2.1 released February 4, 2003. | Formal specification release expected during the first quarter of 2005. |
| Relevant organization | PXI Systems Alliance, www.pxisa.org | LXI Consortium, www.lxistandard.org |
