COM Express® is a PICMG standard that defines a Computer-On-Module, or COM, packaged as a super component. The defined interfaces provide a smooth transition path from legacy parallel interfaces to LVDS (Low Voltage Differential Signaling) interfaces. This includes the PCI bus, parallel ATA, PCI Express and Serial ATA. COM Express®® defines 5 different pinout types in order to be scalable for future applications.
PICMG is a consortium of over 450 companies who collaboratively develop open specifications for high performance telecommunications and industrial computing applications. The members of the consortium have a long history of developing leading edge products for these industries.
A high level of compatibility allows that a carrier board designed to accommodate a Basic module can also support a Compact module. The type 2 connector layout is available for all board sizes. It defines 440 interconnect pins between the COM Express® module and the carrier board. Legacy buses such as PCI, parallel ATA and LPC are supported along with new serial high speed interfaces such as PCI Express, Serial ATA and Gigabit Ethernet.
COM Express® is a legacy free standard. Outdated interfaces such as floppy, PS/2 keyboard/mouse, RS232, LPT are no longer supported. If required, these legacy interfaces can be optionally generated on the customized carrier board.
The PICMG has defined two module sizes: the Basic module (125x95 mm?) and the Extended module (155x110 mm?). The primary difference between the Basic module and the Extended module is the overall physical size and the performance envelope supported by each. The Extended module is bigger and can support more power consuming processors and chips with larger footprints.
As with XTX? and ETX?, the COM Express® definition includes a heatspreader that acts as a thermal interface between the COM Express® module and the system?s cooling solution. The height of a COM Express® module, including the heatspreader, has been defined as 18 mm and covers the complete area of the Embedded Computer module. All heat generating components are thermally conducted to the heatspreader in order to avoid hot spots.
In addition to the 32 bit parallel PCI bus, COM Express® offers up to 22 PCI Express? lanes. This allows the customer to equip their embedded PC application with the next generation of PC performance. PCI Express? is a low pin count interface with maximum bandwidth per pin. This results in cost optimization and very compact solutions with the highest I/O performance. The scalable bandwidth is 2.5 GBit/s per lane and direction.
PCI Express Graphics (PEG)
The PEG interface utilizes up to 16 PCI Express lanes in order to drive an external high performance graphic controller located on the carrier board. Ultra high graphics performance suitable for gaming applications can be implemented using the PEG interface.
COM Express® supports ExpressCard? slots. ExpressCard? is the successor to PCMCIA. This interface allows the use of USB 2.0 and PCI Express? applications as well. The ExpressCard? standard offers a new performance class in a small package.
4x Serial ATA Interfaces
Serial ATA is an enhancement of the parallel ATA therefore offering higher performance. As a result of this enhancement the traditional restrictions of parallel ATA are overcome with respect to speed and EMI. Serial ATA starts with a transfer rate of 150 Mbytes/s and can be expanded up to 600 Mbytes/s in order to accommodate future developments. Serial ATA is software compatible to parallel ATA.
Digital Audio Interface
COM Express® offers a digital audio interface for AC?97 or High Definition Audio codecs (HDA). The following features are available:
- DVD Audio
- Multi Stream Capabilities
- Telephony (VoIP)
- Dolby 5.1/6.1/7.1
- Dynamic Connector Configuration
COM Express® can utilize several audio codecs. This allows for the easy implementation of telephone and audio applications that require the highest sound quality and numerous channels.
COM Express® defines freely usable general purpose inputs and outputs. These GPIOs provide very good flexibility for custom applications.
For easy connection of low speed devices, COM Express® offers the LPC (Low Pin Count) bus. There are many devices available for this Intel defined bus. The LPC bus corresponds approximately to a serialized ISA bus yet with a significantly reduced number of pins. Due to the software compatibility to the ISA bus, I/O extensions such as serial ports can be easily implemented using the LPC bus.
High Speed USB
COM Express® offers up to eight USB 2.0 ports. This provides maximize connectivity for your embedded solution.
COM Express® Type 2 supports one gigabit Ethernet port. The type 3 defines up to three gigabit Ethernet connections.
This new concept will permit easy integration while providing the latest I/O interface technologies and will also enable large headroom for future applications.