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High-Speed Throughput and Processing Drive XMC and PrXMC Trends

Today’s XMCs and Processor-based PrXMCs offer fabric-based interconnects suited for high-speed processing as well as numerous types multi-function I/O solutions.


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XMCs and Processor XMCs (PrXMCs) are now firmly entrenched as the natural heirs to the venerated PCI-based PMC and Processor PMC (PrPMC). XMCs enable system developers to mix and match the functions they need and by doing so create a semi-custom solution using off-the-shelf products. Meanwhile, processor-based mezzanines like PrXMCs advance the idea of separating computing functions from I/O, and application-specific functions have become a core theme in military applications. That concept is very attractive for applications with long design cycles like the military.

The VITA 42 XMC set of standards provides backward compatibility with legacy PMC modules while allowing PCI bus products to integrate switched fabric architectures. The standards build on the existing PMC standards by adding switched fabric interconnects to the existing PCI bus interface. XMC has a conduction-cooled option that piggybacks off the VITA 20 Conduction-Cooled PMC standard.

The VITA 42.0 base specification does not dictate signal types, data rates, protocols, voltage levels or grouping for these signals. Instead, it leaves that up to the several sub-specifications that are part of the VITA 42 family. This allows XMCs to evolve as new interconnect technologies and protocols emerge. To support gigabit serial interfaces, notice that both P15 and P16 connectors define 10 full-duplex differential pair lines.

As the product listings on the follow several pages show, advanced processing chips like GPUs, FPGAs and even Intel Xeon processors are now common on XMC and PrXMC offerings.  FPGAs have become a particular fixture in mezzanine card designs. The latest crop of XMC boards sports powerful FPGAs like the Xilinx Artix -7 and Kintex UltraScale. These FPGAs offer a collection of resources ideally suited for DSP and peripheral I/O functions. FPGAs may be configured to implement numerous electrical interface standards as well as a variety of protocol engines.

Thanks to the magic of today's level of semiconductor integration, multifunction board products have emerged enabling military system designers to blend a variety of I/O functions onto a single XMC card. The challenge has been to choose I/O technologies that are suited for use together. Reconfigurable FPGAs can be used to enable an I/O board to replace several legacy products, while adapting to future standards and protocols as well. This helps to mitigate product obsolescence, both at the board level and at the deployed system level.

In applications that depended heavily on signal acquisition, raw resolution and bandwidth are only effective if the analog front end and the acquisition subsystem maintain good signal integrity as the signal is moved into the digital domain for processing. Here, XMC mezzanines help that issue as the analog components can be physically on a separate card from the digital processing components on the carrier card. An example of a system making use of XMC-based solutions is the E-2D Advanced Hawkeye (Figure 1). Using XMC technology, the data recording and playback systems for the E-2D could scale up to dozens of modular, heterogeneous input/output channels and FPGA-based protocol engines.

Figure 1
An E-2D Hawkeye 125 launches from the flight deck of the aircraft carrier USS Theodore Roosevelt (CVN 71).

The XMCs and PrPMCs Roundup and Links to the full data sheets for each product are posted on the roundup part of this section. Click here for the roundup.