Pxi Slots

PXI tutorial includes:
What is PXI?PXI standardPXI chassisPXI bus and backplanePXI controllerPXI cards & modulesPXI softwarePXI ExpressPXImc MultiComputingSet-up & build PXI system

PXI peripheral slots will accept PXI cards of the standard connector types- those that work in current non-express PXI chassis. PXI Express Hybrid slots, due to the hybrid or combination of backplane connectors, accept PXI Express cards, 32-bit CompactPCI cards, and Hybrid Compatible PXI cards (also known as PXI Express-ready or PXIe-ready). PXI Express Desktop Chassis, 4 U, 44 HP 1 PXIe System slot an 7 Hybrid slots Ultra-high performance Gen 3 PCIe switching with a default four-link (4x4) system slot Powerful cooling concept with low fan noise, 50 W per slot @ 15K temperature increase.

The PXI bus system enables the overall PXI technology to offer a great amount of flexibility in terms of controlling the different instrumentation cards that are available. In view of this, the PXI test instrumentation system is used in a wide variety of applications from automatic test equipment to data acquisition.

The bus is carried along the PXI backplane. This not only links the PXI bus to the individual cards, but also supplies other essentials such as power to the cards.

PXI bus basics

Although the PXI system is based around the PCI standard, this system cannot be used directly in this format. Many test equipment and data acquisition applications require accurate timing capabilities and clocks that cannot be implemented using the standard PC specifications including PCI and CompactPCI (cPCI) as well as ISA. The reason for this is that there is no reference clock. The PXI bus system builds on the basic PCI standard and implements these in the form of a dedicated system clock and triggers. These features include the following:

• PXI bus reference clock
• PXI Local bus
• PXI trigger bus
• PXI star trigger bus
• Slot to slot local bus

In addition to this the specification defines a slot for the PXI system controller.

PXI bus system slot

The position of what is termed a PXI system slot is defined. The location of this is on the left end of the PCI bus segment in a basic PXI system. This arrangement is a subset of the numerous possible configurations allowed by CompactPCI where it may be anywhere on the back plane. Defining a specific location for the system slot provides a number of advantages including a simplification of integration and an increase in the degree of compatibility between PXI controllers and chassis. Also the PXI specification requires that where necessary the system controller module is able to expand to the left into what are defined as controller expansion slots. By carrying this expansion to the left this prevents the system controllers from using up valuable peripheral slots.

PXI bus reference clock

In many applications it is necessary to accurately synchronise measurements or other actions to a single clock. The PXI standard allows for this by proving a 10 MHz TTL reference clock.

The basic accuracy of the reference clock not mandated by the standard and is dependent upon the actual oscillator fitted to the chassis. Typically it will be better than 25 ppm. However the standard does specify that the track lengths from the oscillator shall be the same so that the skew between the edges reaching the different cards is less than 1 pS. This is important to ensure that triggering relative to the operation of the overall system remains constant.

PXI Local bus

A third form of PXI bus is known as the local bus. This receives its name because it is a daisy chain bus that connects one slot with the adjacent slots. The bus is 13 lines wide, and allows both digital and analogue (up to 42 volts) signals to be passed over it. In this way signals that may be required to be transferred within the chassis can be accommodated.

PXI bus triggers

There are three triggers that are defined within the PXI standard. Each type defines a different form of trigger capability, enabling the standard to offer a variety of different trigger functions dependent upon the requirements of the measurement.

• PXI Trigger bus: There are many instances where a trigger is required, and the trigger bus can be used for many of these applications. The PXI standard defines a bus consisting of eight separate trigger lines. They enable synchronisation and timing signals to be passed from one module to another where one module may act as a master passing timing or synchronisation to the others that may act as slaves.
  The trigger lines allow triggers, clocks, or handshaking signals to be transferred, although it is recommended that clock signals above 20 MHz are not transferred along this bus because of the signal degradation that may be suffered. Nevertheless the trigger bus is particularly useful for most applications.
• Star trigger bus: The star trigger bus adopts a different approach to that of the ordinary trigger bus. It is used for applications where a high speed trigger with low levels of delay and skew are required. To achieve this, an independent line is routed from what is termed the star trigger slot (slot 2 in the PXI chassis) to each of the other slots in a star configuration. Again the line lengths are matched to ensure that the propagation delays are matched to within 1 pS.

PXI bus power supplies

The PXI backplane carries the power for the various cards within the chassis. The power supplies must naturally be standardised to enable a variety of cards to operate satisfactorily within their allocated slots.

Most VXI chassis support a variety of different supply voltages including +5V, +3.3V as well as +12v and -12V. Supply capabilities vary, but the PXI standard version 2.1 provides for the following capabilities:

In order to remain within the maximum current capability of the pins of 1 amp on the backplane, the high current capacity supplies require multiple pins. For example the 5V system slot +5V supply requires six pins.

With these specifications set down, PXI technology is able to provide a resilient test and data acquisition approach that can meet the needs of a large number of applications within the electronics industry. PXI technology is widely used for general test equipment applications, as well as for test, automation and data acquisition. It is possibly for use within data acquisition systems that it has gained most of its use. For these data acquisition systems it enables a compact flexible system to be created at a reasonable cost. Accordingly PXI has become one of the leading standards for test, measurement and automation.

Pxi Slot Blocker

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PXI tutorial includes:
What is PXI?PXI standardPXI chassisPXI bus and backplanePXI controllerPXI cards & modulesPXI softwarePXI ExpressPXImc MultiComputingSet-up & build PXI system

PXI, PCI eXtensions for Instrumentation, has emerged as a major force in the test equipment and instrumentation industry.

PXI provides a rugged PC based platform for use in automated test, data acquisition and many other applications.

It successfully combines rugged mechanical elements with a high electrical performance specification and a low cost. Using standard PC technology, this makes PXI an ideal platform for a host of applications

What is PXI? - the basics

PXI is based on the popular PC based bus system, CompactPCI, used for embedded development and computer based platforms As such PXI is able provide the benefits of the PCI architecture: high level of performance, industry acceptance, wide availability of off the shelf units, etc. PXI adds a rugged Compact PCI mechanical form-factor, an there is an industry consortium that defines hardware, electrical, software, power and cooling requirements, enabling interconnectivity between items from different manufacturers.

In addition to this, the system adds a number of other capabilities required for test, measurement, data acquisition and control applications. These include aspects including: integrated timing and synchronization that is used to route synchronization clocks, and triggers internally.

A further advantage of PXI is that having been adopted by the industry it will remain in use for many years to come, thereby enabling any investment to be protected. These advantages make PXI an ideal standard for use as test equipment and for data acquisition applications. Read more about the PXI standard & specifications.

PXI Hardware

The PXI hardware is platform on which the overall PXI standard is based. It forms the platform for running the software and for the individual instruments. It forms a particularly flexible scheme allowing a very wide variety of instruments to operate within a chassis environment.

There are three basic elements to a PXI system:

• PXI Chassis: The chassis is the most visible element of the system. The PXI chassis literally provides the framework for the system and it normally can range in size from four slots up to eighteen.
  The PXI chassis contains a high performance backplane enabling the cards in the system to be able to communicate rapidly with one another and in addition to this timing and triggering lines are also included.
  To put this in context, a typical 3U PXI module measures approximately 100 x 160 mm (4x6 inches), and a typical 8-slot chassis is 4U high and half rack width, full width chassis contain up to 18 PXI slots.
• System controller: A system controller card is located in left hand slot in the rack, or alternatively control can be undertaken by a remote PC. The use of a standard PC provides a particularly cost effective, but powerful option for many users.
  In this way the convenience of a standard PC can be combined with the power that they are able to offer these days. However the use of a controller module is also convenient in many applications and these leverage on the wide variety of PC cards and modules that are available.
  Read more about . . . . PXI controller.
• Modules or instruments that slot into the chassis: There is a very wide variety of modules that are available. They include test instruments for taking a wide variety of measurements, e.g. voltage, current, frequency as well as signal and waveform generators. However modules are also available to perform other functions including boundary scan testing, digital or analogue input and output, image acquisition, power supplies, switching and much more.
  By choosing modules to meet the requirements of the overall PXI system it is possible to build up a flexible test or automation system that can be easily tailored to meet virtually any requirement.

PXI software

Many PXI instrument modules or cards are register based items. They use software drivers that can be hosted on the central controller PC and these configure in the way that the PXI modules are set up for the particular application in question. By adopting this technique it enables them to provide considerably more flexibility as the controller PC is able access the instrument directly and this simplifies the embedded software in the modules while enabling a high level of flexibility to be obtained. The open architecture allows hardware to be reconfigured to provide new facilities and features that are difficult to emulate in comparable bench instruments.

Pci Slots X16

In addition to this a number of vendors offer software to run the automated tests and data acquisition applications. These proprietary products provide a high degree of sophistication, while being designed to operate with PXI. In addition to this they can be configured to meet the requirements of an individual application, be it for automated test, or data acquisition.

Major features of PXI technology

The PXI system boasts many features that make it a flexible platform for many applications. The highlight features of the PXI standard are detailed in the table below:

Pci Slots Test

The PXI standard is a particularly successful open architecture test equipment standard that is widely used for a variety of applications. The system can be used to provide automated test, as well as fulfilling a variety of other data acquisition requirements. This makes PXI an ideal standard to be considered where automated test and data-logging are needed.

More Test Topics:
Data network analyzerDigital MultimeterFrequency counterOscilloscopeSignal generatorsSpectrum analyzerLCR meterDip meter, GDOLogic analyzerRF power meterRF signal generatorLogic probePAT testing & testersTime domain reflectometerVector network analyzerPXIGPIB Boundary scan / JTAG
Return to Test menu . . .