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PXI vs LXI vs VXI vs MXI-Difference between PXI LXI VXI MXI

This page on PXI vs LXI vs VXI mentions basic difference between PXI,LXI,VXI,MXI interfaces.The difference between various terms and serial interfaces are also mentioned. All these terms are evolution of communications between the instruments in test and measurement domain. These interface buses will help in achieving interoperability and synchronization needs as well as data transfer requirements between the instruments.

Both PXI and LXI has unique features and hence test and system integration engineers need to choose the interface as per the application and performance need. Refer following for the difference between PXI and LXI.

PXI interface

Following are the details of PXI interface:
• Full Form: PCI eXtensions for Instrumentation
• It is based on PCI bus architecture.
• Utilizes central processing model of the PC
• It's size is module dependent.
• The modules will have inter-connection overheads.
• It requires add on software.
• The implementation of PXI system is cumbersome and not so cost effective.
• It utilizes 132 Mbytes/sec bandwidth of PCI.
• Transfer width: 8/16/32/64 bits
• Throughput: max. 12 Gbps
• EMI shields are required as per module size
• Supports modularity

LXI interface

It has been designed to provide communication between ethernet based instruments. The LXI interface standard is developed based on ethernet standard, web interfaces and IEEE-1588 standard. Initially LXI ver 1.0 is introduced in 2005. Later on continuous improvements have been made to the LXI specifications. Hence versions 1.1,1.2,1.3 and 1.4 have been introduced. Power supplies are designed as per LXI specifications. LXI instruments support upto 100Mbps.

Following are the details of LXI interface:
• Full Form: LAN based eXtensions for Instrumentation
• It is distributed system. The communication between the instruments is message based.
• LXI has size freedom and can be vendor requirement specific to obtain the required performance.

VXI interface

It has been designed to provide following:
• high density platform through shared resources
• Concise timing co-ordination between various instruments

Following are the details of VXI interface:
• Full Form: VME eXtensions for instrumentation based on IEEE-STD-1155
• Introduction year: 1987
• It is based on VMEbus architecture.
• It utilizes 40 Mbytes/sec bandwidth of standard VME.
• Transfer width: 8/16/32 bits
• Throughput : max. 160 Mbytes/sec
• Need VXI plug and play
• Supports modularity
• EMI shielding is defined

Following table provides difference between PXI and VXI interfaces:

Specifications PXI VXI
Local Bus 13 lines 12 lines
Clock 10 MHz (TTL Based) 10 MHz (ECL) and 100 MHz (D-Size)
Star Bus 1 per slot D-size only
Triggers 8 TTL 8 TTL, 2 ECL, 4 additional ECL(D-size)

MXI interface

This bus interface was designed and developed by NI(National Instruments) in 1989. Similar to VXI, it has been derived from VMEbus. It has been later enhanced as MXI-2 standard in the year 1995.

With this MXI bus interface, computer can be directly accessed next to VXI or within 20 meters coverage.

Following are the details of MXI interface:
• Full Form: Multisystem eXtension Interface
• Transfer width: 8/16/32 bits
• About 8 MXI devices can be daisy chained on a single MXI cable length(supports length of 20 meters).
• It is an open standard

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