The COM Express® standard was first released in 2005 as the open industry standard for Computer-On-Module by the PCI Industrial Computer Manufacturers Group (PICMG). The COM Express® standard has worked to provide standardized module interfaces for several different target industries such as industrial automation, gaming, defense and aerospace, medical, retail, advertising, etc.
A COM requires a baseboard to provide I/O functions and to power up. COMs are used to build single board computer solutions and offer OEMs fast time-to-market with reduced development cost. Like integrated circuits, they provide OEMs with significant freedom in meeting form-fit-function requirements. For all these reasons the COM methodology has gained much popularity with OEMs in the embedded industry.
The COM Express® standard has key features including rich high bandwidth serial interfaces such as PCI Express, Serial ATA, USB 3.0 and Gigabit Ethernet. It also supports extensive video port including VGA, LVDS, DP, DVI and HDMI termination drivers plus x16 PEG port to carrier board graphic controller.
Systems based on the COM Express® specification require the implementation of an application-specific carrier board that accepts the module. User-specific features such as external connector choices and locations and peripheral circuits can be tailored to suit the application, so that the OEM can focus on application-specific features rather than CPU board design. The OEM also benefits from a wide choice of modules providing a scalable range of price and performance upgrade options.
COM Express® Specification
The COM Express® specification defines requirements for highly integrated slim modules with standard I/O interfaces and connections, which allows interoperability between multi-sourced modules. Key capabilities defined in the COM Express® specification include support for:
* PCI Express Bus
* PCI Express Graphics (PEG)
* Serial ATA
* USB 2.0/3.0
* Gigabit Ethernet
* DDI Interface
The COM Express® specification defines four form factors:
* Mini (84 x 55 mm) Module
* Compact (95 x 95 mm) Module
* Basic (125 x 95 mm) Module
* Extended (155 x 110 mm) Module
The Mini Module targets the next generation of mobile applications that require energy saving processors, high-end graphics combined with longer battery life. Compact/Basic Modules usually use a single (or two stacked) horizontal mount SO-DIMM. The mechanical envelope for the Basic Module is defined for low-profile, space-constrained applications. Figure 1 shows COM Express® form factors and Axiomtek COM Express modules.
COM Express® Interface Signals
Axiomtek COM Express Type 6 Modules apply to the Compact and Basic form factors and Type 10 Modules apply to the Mini form factor:
* Module Types 2/6 supports two connectors with four rows of pins (440 pins total)
* Module Type 10 supports a single connector with two rows of pins (220 pins total)
Connector placement and most mounting holes have transparency between form factors. The features among the Module Type 2/6/10 are summarized in Table 2-1.
COM Express® Type 2/6/10 required and optional features are summarized in Table 2-2 and Table 2-3.
Axiomtek COM Express® Type 6 Module
Following the COM Express® specification, Axiomtek released two form factors of COM Express® Type 6 Modules. The COM Express® Type 6 Basic Module CEM880 features 5th Generation Intel® quad-core i7 processors (Broadwell) or 4th Generation Intel® quad/dual-core™ i7/i5/i3 or Celeron® processors (Haswell) and Intel® QM87 chipset. The COM Express® Type 6 Compact Module CEM881 features 5th or 4th Generation Intel® quad/dual-core™ i7/i5/i3 or Celeron® processors (Broadwell / Haswell-ULT SoC). Both of them can carry up 4GB onboard memory and support industrial temperature -40°C to +85°C (-40°F to +185°F). With 5th/4th Generation Intel® Core™ or Celeron® processor, the CEM880 and CEM881 are designed to provide excellent graphics and performance, supporting contemporary high bandwidth serial interfaces including PCI Express, SATA, USB 3.0 and Gigabit Ethernet. These rugged SOMs (System on Module) are ideal for graphics-intensive, rich I/O and harsh applications.
Technical Support by Axiomtek
The Axiomtek design guide for COM Express® carrier boards serves as a general guide for carrier board designs. The design guide focuses on maximum flexibility to accommodate a range of COM Express® Modules. The Axiomtek COM Express® design guide explores the requirements of the COM Express® specification and provides recommendations on how to design COM Express® Baseboards to support features of Axiomtek COM Express® Modules.
The carrier board design guide provides schematic examples and information on standard I/O interfaces, connections, and routing. The guide also offers ideas to maximize the design potential of COM Express® carrier boards to accommodate all Axiomtek COM Express® Modules.
The COM Express® Module user guides documents provide specifications and features for an individual COM Express® Module. You can find all user guides, design guides, mechanical drawings and other technical documents for COM Express® Modules on the Axiomtek Technical Portal (ATP) Website.
Axiomtek’s ATP website: http://atp.axiomtek.com.tw/atp/
Axiomtek’s global website: www.axiomtek.com