For decades now, the notion of standards-based slot card embedded computing has been a tried and true mainstay of military electronics. Lead by bus architectures such as VME and CompactPCI, the traditional approach is to use slot-card boards in a card cage. This means choosing a bus architecture, a rugged card cage and an SBC, plus any additional I/O boards to fulfill the requirements. But as semiconductor integration continues to enable more complete systems on one or two boards, the emergence of busless Computer-on-Module (COM) technologies is starting to gain some attention in the military market. COM boards provide a complete computing core that can be upgraded when needed leaving the application-specific I/O on the baseboard. COM Express adds high-speed fabric interconnects to the mix.

As complete systems become more doable using those technologies, they’re beginning to replace some platforms that once relied on slot-card systems like VME and cPCI. But for many military applications, the advantages of a slot-card approach take precedence. In the case of a tech refresh or tech upgrade program, the bus architecture is already given—VME being the most prevalent for military applications. More recently, for applications where size, weight and power have priority over past compatibility with legacy boards, the option of rugged box-level systems that are basically monolithic integrated computers is popular.

Tried and True Slot-Card Approach

The slot-card approach brings with it a number of merits. It offers the greatest flexibility in the I/O complement that can be supported. If a MIL-STD-1553 interface is needed, such a board can be added. The flexibility of a slot-card system is particularly useful when not all the I/O requirements are defined at the beginning of a project—a situation not uncommon in military programs. Moreover, some applications like comms and networking systems often require slots left open for the end-user for reconfiguring systems functionality in the field (Figure 1). Military-focused slot-card technologies continue to advance. Follow-on standards to VME such as OpenVPX ensure a solid future for the slot-card approach.

While it’s clear that slot-card embedded systems aren’t going away anytime soon, COM-based busless system architectures are carving out a place in military mindshare. Just one COM Express module can provide the same processing and graphics performance as alternative solutions. Designers have three COM Express module sizes to choose from to suit their individual application requirements. All signals are maintained on the carrier card, where additional connectors can be added as required per specific applications. As a macro-component, COM Express enables technology insertions without a large time or monetary investment, and supports easy upgrades through multiple product lifetimes.

Small and Flexible

Last summer, PICMG released the COM Express Revision 2.0 specification. The rev 2.0 specification allows developers to focus on their specialized I/O requirements, without worrying about the complex interactions of CPUs, RAM, Chipsets and other basic elements that occur on the module. This recent revision helps to ensure that COM Express modules are prepared for future computer architectures while accommodating backward compatibility with older modules. The more important changes include smaller size, enhanced display support, faster Generation 2.0 PCI Express ports, high-definition audio and USB client support.

One of the smallest COM Express offerings available is Kontron’s COM Express-compatible module (55 mm x 84 mm), the COM nanoETXexpress-TT (Figure 2). Sporting the new Intel Atom processor E6XX, the card is also equipped with the newly defined PICMG COM Express COM.0.R.2 Type 10 pin-out that was added to the COM.0 R2.0 specification. With industrial-grade components, functional in the range of -40° to +85°C and with different options for data storage, it is suitable for use in harsh environments and thus complements the existing portfolio. The card has four PCI Express lanes of which three can be used for dedicated application-specific interfaces. This enables the use of even more dedicated mini-devices in a semi-custom solution.

In addition to LVDS, it offers the newly implemented Digital Display Interface (DDI) for SDVO, Display Port or HDMI, which allows two displays to be controlled independently. The module also supports two different options for data storage: either a robust micro-SD Card socket offering up to 32 Gbytes and 2x SATA II 300 Mbyte/s interfaces, or a planned version with industrial-grade SATA Flash Memory (up to 16 Gbytes) and 1x SATA II 300 Mbyte/s connector.

Video and Comms for UAVs

With recent improvements in video support and chipset graphics, integrated video support has become a mandatory requirement for UAVs and other military systems. COM Express planned for the expansion of video and display capabilities, and provides standard connector access for a variety of high-speed interfaces. The COM Express connector supports multiple video interfaces including DisplayPort, VGA, SDVO, HDMI or DVI. This allows designers to take advantage of the latest graphics capabilities without having to worry about affecting performance.

COM Express was specifically designed to ease the transition from legacy connectors and offers native interface support for modern-day I/O interfaces. On top of offering more PCI Express and USB ports than PC/104-Express modules, additional connecters can be added for LAN, SATA, video, audio, USB and PCI Express, delivering maximum I/O flexibility to meet specific application requirements. And since signals do not have to pass through multiple connectors, the signal integrity remains intact. 

As the computing demands for systems such as UAVs continue to increase, that’s driving a need for higher performance, faster I/O, improved graphics and lower support costs. Today’s growing demand for network-centric capabilities makes it an ideal time for developers to adopt COM Express. The standard’s flexible, two-board architecture makes COM Express an ideal solution for today’s most demanding UAV applications (Figure 3), and can help designers take advantage of the latest technologies at lower costs.

Combining COM and Slot-Card Approaches

The concepts of a non-backplane COM approach and a backplane-based slot-card strategy seem like separate directions. But the idea has emerged recently of using COM boards as computing core upgrades on slot-card SBCs. RadiSys, for its part, has pushed the idea of placing Computer-on-Modules (COMs) on VPX boards, allowing equipment developers to easily implement the latest computing technologies while preserving their VPX board development investments. RadiSys makes this case in an article in last September’s issue of COTS Journal in an article titled “The Case for Blending COM Express and VPX.”

That same idea is being used for the ATCA form factor. ATCA has carved out a respectable niche in the military where high-density computing and net-centric communications are a priority. An ATCA blade offering from Adlink technology is an example. Called the aTCA-3150 (Figure 4), this board provides a COM Express Type 2 site for expansion with a processing subsystem, allowing users to tailor processing power to application demands. In addition, two mid-sized AMC bays for I/O expansion are also supported to suit the needs of different applications. The aTCA-3150 provides 10/100/1000Base-TX GbE and layer 3 switching on Base Interface with support for 14-slot shelves.  

ADLINK
San Jose, CA.
(408) 360-0200.
[www.adlinktech.com].

Kontron
Poway, CA.
(888) 294-4558.
[www.kontron.com].

RadiSys
Hillsboro, OR.
(503) 615-1100.
[www.radisys.com].