An Overview of the PXI Platform (2024)

As defined by the PXI Hardware Specification, all PXI chassis contain a system controller slot located in the leftmost slot of the chassis (slot 1). Controller options include remote control modules that allow PXI system control from a desktop, workstation, server, or laptop computer as well as high-performance embedded controllers with either a Microsoft OS (Windows 7/10) or a real-time OS (LabVIEW Real-Time).

PXI Embedded Controllers

PXI embedded controllers eliminate the need for an external PC and provide a high-performance, yet compact in-chassis embedded computer solution for your PXI or PXI Express measurement system. These embedded controllers have extended temperature, shock, and vibration specifications and come with an extensive feature list such as the latest integrated CPUs, hard drive, memory, Ethernet, video, serial, USB, and other peripherals. By providing these peripherals on the controller’s front panel, overall system cost is minimized because you don’t need to purchase individual PXI or PXI Express cards to gain similar functionality. The controller comes pre-configured with LabVIEW Real-Time or Microsoft Windows and all the device drivers pre-installed. NI’s embedded controllers also have managed life cycles and offer vendor support to ensure test system longevity and compatibility with the PXI ecosystem.

PXI embedded controllers are typically built using standard PC components in a small PXI package. Performance benchmarking done by NI R&D also ensures the development of controllers that are optimized for test and measurement applications to guarantee that code and algorithms run faster. For example, the PXIe-8880 has a 2.3 GHz eight-core Intel Xeon E5-2618L v3 processor (3.4 GHz maximum in single-core, Turbo Boost mode), up to 24 GB of DDR4 RAM, solid-state drive, two Gigabit Ethernet ports, SMB trigger, and standard PC peripherals like two USB 3.0 ports, four USB 2.0 ports, DisplayPort, and GPIB.

When NI releases a new PXI embedded controller, it offers the controller shortly after major computer manufacturers like Dell or HP release computers featuring the same high-performance embedded mobile processor. Because NI has been in the business of releasing PXI embedded controllers for more than 15 years, the company has developed a close working relationship with key processor manufacturers such as Intel and Advanced Micro Devices (AMD). For example, NI is an associate member of the Intel Embedded Alliance, which offers access to the latest Intel product roadmaps and samples.

^{Figura 7: The PXIe-8880 embedded controller, featuring the eight-core Intel Xeon E5 processor, is ideal for high-performance, high-throughput, and computationally intensive test and measurement applications.}

In addition to computing performance, I/O bandwidth plays a critical role in designing instrumentation systems. As modern test and measurement systems become more complex, there is a growing need to exchange more and more data between the instruments and the system controller.With the introduction of PCI Express and PXI Express, NI embedded controllers have met this need and now deliver up to 24 GB/s of system bandwidth to the PXI Express chassis backplane.

^{Figure 8: NI has continued to deliver the latest and most powerful processing technology to the PXI platform for the last 20 years.}

Rack-Mount Controllers

To provide an alternative computing and control option, NI offers external 1U rack-mount controllers. They feature high-performance multicore processors for intensive computation and multiple removable hard drives for high data storage capacity and high-speed streaming to disk. These controllers are designed to be used with MXI-Express and MXI-4 remote controllers for interfacing to PXI or PXI Express chassis. In this configuration, the PXI/PXI Express devices in the PXI system appear as local PCI/PCI Express devices in the rack-mount controller.

^{Figure 9: Rack-mount controllers with MXI-Express or MXI-4 remote controllers can be used to control PXI or PXI Express chassis.}

PC Control of PXI

Through MXI-Express technology, PXI Remote Control Modules provide a simple, transparent connection between a host machine, like a desktop PC, and the PXI chassis and instruments. During start-up, the computer recognizes all peripheral modules in the PXI system as PCI boards, allowing further interaction with these devices through the controller. PC control of PXI consists of a PCI/PCI Express board in your computer and a PXI/PXI Express module in slot one of your PXI system, connected by a copper or fiber-optic cable. Copper cables offer higher data throughput capability, but are generally shorter (1 to 10 meters), while fiber-optic cables are available in much longer options (up to 100 meters), but may have lower data throughput capability. Most PCs are immediately compatible with PXI remote control solutions. Furthermore, compatibility with MXI-Express devices is ext ended to even more PCs through NI's MXI-Express Bios Compatibility Software.

Laptop Control of PXI

You can equivalently control a PXI Express system from a laptop computer using the PXIe-8301 remote control module from National Instruments. Laptop control of PXI Express consists of a PXI Express module in slot one of your chassis and a Thunderbolt 3™ cable connected to your laptop.

^{Figure 10: Remote control modules enable desktop control of one or more PXI chassis.}

^{Figure 11: The PXIe-8301 remote control module is ideal for ultra-portable applications.}

Multichassis Configurations

Multichassis configurations allow two or more PXI chassis to be managed by a single master controller. As a unified system, multiple chassis can take advantage of benefits such as cross-chassis synchronization, separation of instrument types to optimize data throughput, and peer-to-peer transfers between instruments in separate chassis.

The most common method of forming a multichassis system is through daisy chaining. A daisy-chain topology consists of one or more slave (downstream) chassis connected in series to a master (upstream) chassis that is controlled through a PC or PXI embedded controller. When using a daisy-chain topology, each slave chassis is visible to and controllable by the host machine.

^{Figure 12: A PXIe-8364 host interface module is placed in a peripheral slot of the master chassis containing an embedded controller. An additional chassis is daisy chained by connecting the PXIe-8364 to a PXIe-8360 in the system controller slot of the slave chassis. Additional modules may be used to daisy chain up to eight chassis.}

While the above solution requires an additional module in a peripheral slot for daisy chaining, some PXI Remote Control Modules contain built-in daisy-chaining capability through the inclusion of two ports—one for an upstream connection and one for a downstream connection.

^{Figure 13: A desktop PC with a PCIe-8375 is connected to a master PXI Express chassis through a PXIe-8375 remote control module. The PXIe-8375 features an additional port for daisy chaining, requiring only an additional PXIe-8375. The last downstream chassis in this system will have an unused port.}

Some host interface cards contain two downstream ports, allowing for a star topology. Rather than connecting two slave chassis in series (daisy chain), the star topology connects two slave chassis in parallel, allowing each chassis to communicate directly to the host rather than through an intermediary chassis.

^{Figure 14: The PCIe-8362 host interface card contains two MXI-Express connections, allowing two PXI Express chassis to be controlled through a desktop PC using a star topology.}