EMX FAQ

This page addresses various questions and considerations associated with using EmbeddedXpress (EMX) technology in embedded systems applications. Feel free to add your own questions or comments in the comments area below.

 


EMX FAQ Questions


Click each question to read the answers below…

Q1: What is the purpose of EMX? Why create a new form factor that’s incompatible with other products already on the market?

Q2: Why doesn’t the number of ground pins equal the sum of all the other power pins?

Q3: Why doesn’t EMX offer PCIe x4 and x16? Will it be possible to add them in the future?

Q4: What are the supply voltages used on EMX?

Q5: How rugged is EMX?

Q6: Why not use PCIe/104 or Sumit as the expansion buses instead of the EMX bus connector?

Q7: Won’t the lack of a PC/104 / PCI-104 / PCIe/104 connector limit the usefulness of EMX?

Q8: Are there any royalties or licensing requirements associated with designing or manufacturing EMX-compatible products?
 


EMX FAQ Answers


Q1: What is the purpose of EMX? Why create a new form factor that’s incompatible with other products already on the market?

A1: EMX was created out of the desire to offer greater efficiency, lower overall cost, improved business efficiency, faster time to market, and greater lifecycle benefits to customers and vendors. The design of EMX resulted from several observations about the small form factor market:

  • Currently available small form factor stackable systems are too small to support many newer chipsets, with the result that many vendors use PCB extensions (“wings”), specialty high-density I/O connectors, or I/O breakout boards in order to create a full-featured product. It was desired to avoid these pitfalls by selecting a slightly larger board size.
  • COM modules offer significant advantages over traditional SBCs, including a wide variety of physically compatible modules, a wide range of processor choices in the exact same form factor, performance scalability, and longer product lifetime by the simple replacement of an end of life module with a newer one. A key goal of EMX was to create a standard that utilized COM modules as the CPU engine in order to achieve these benefits for both vendors and customers.
  • COM Express is extremely popular and offers a wide range of processor options in a compatible and compact format. It was decided to adopt the COM Express form factor in order to make it easy to use these modules in a COM-based SBC form factor.
  • PCIe/104 and SUMIT expansion connectors were considered to be too large and expensive, and SUMIT offers too few expansion interfaces. So a new expansion connector was desired for increased economy and reduced PCB area utilization.
  • The mounting holes of PCIe104 and SUMIT formats are incompatible with COM Express, so using one of these formats would have required adding 4 more mounting holes, which would use up precious PCB space. Therefore it was decided to adopt a COM Express form factor for the I/O modules as well.

The answer was to design a new form factor that matches the physical format of COM Express for both CPU and I/O modules, and to select a new, high-density, low-cost connector for the expansion bus.


Q2: Why doesn’t the number of ground pins equal the sum of all the other power pins?

A2: Most applications will not require maximum power on all 3 voltages: 12V, 5V, and 3.3V. Therefore to reduce the number of pins on the I/O connector occupied by power and ground, it was decided to reduce the number of ground pins to a quantity needed to support most applications. Since there are a large number of unassigned pins on the connector, it’s possible in the future to redefine one or more of these pins as ground if the EMX governing body finds it necessary.


Q3: Why doesn’t EMX offer PCIe x4 and x16? Will it be possible to add them in the future?

A3: PCIe x4 and x16 are rarely used in small form factor applications, so the connector and board space costs of providing them were not deemed a high priority. The EMX form factor can accommodate a second high density connector, allowing us to add these features to the standard in the future, given sufficient demand.


Q4: What are the supply voltages used on EMX?

A4: EMX standard system supply voltage is 5V. For products using COM Express modules, the baseboard must supply 12V to the COM express module. This can either be generated by the baseboard or passed through from an external power supply. Finally, EMX I/O modules may be powered by either 5V or 3.3V, since both voltages are present on the EMX expansion connector.


Q5: How rugged is EMX?

A5: EMX has been tested according to MIL-STD-202G method 214-I.


Q6: Why not use PCIe/104 or Sumit as the expansion buses instead of the EMX bus connector?

A6: Connectors are too large and expensive, lane select circuit uses PCB area and adds cost, mounting holes incompatible with COM Express and therefore consume still more PCB area. See comparison chart.


Q7: Won’t the lack of a PC/104 / PCI-104 / PCIe/104 connector limit the usefulness of EMX?

A7: Many of the most popular categories of I/O are already available in the EMX format. A FeaturePak carrier also makes it easy to adopt other I/O modules into the EMX ecosystem without requiring any additional development. Like all standards, in the beginning the number of available I/O modules is small, but it will grow over time. For situations where a customer needs a particular PC/104 or PCIe/104 I/O module, a carrier module can be created to convert from EMX to PC/104, PCIe/104, or SUMIT.


Q8: Are there any royalties or licensing requirements associated with designing or manufacturing EMX-compatible products?

A8: EmbeddedXpress (EMX) is an open standard, freely usable with no licenses or royalties. Quoting from the EMX Specification…

    “EmbeddedXpress” and “EMX” are trademarks of Diamond Systems Corporation. The EMX standard and any related logo are the intellectual property of Diamond Systems Corporation. The standard may be used freely in perpetuity by anyone without payment of any royalties or licenses to Diamond Systems Corporation.

Additionally…

    Use of the name and any related logo is granted by Diamond Systems Corporation to all users who make a good faith effort to comply with the standard. Diamond Systems Corporation has sole rights to determine whether any claim regarding EMX compatibility is justified and merits use of the name and logo. Proper trademark attribution must be made in connection with any usage of the standard, name, and/or logo.

For more details, consult the EMX Specification.


 

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