Express104 spec boosts stackable module design - Embedded.com

Express104 spec boosts stackable module design

SAN JOSE, Calif. — The Small Form Factor Special Interest Group (SFF-SIG) released the details of the Express104 specification at the Embedded Systems Conference here.

It defines a small stackable module form factor utilizing the SUMIT (stackable unified module interconnect technology) expansion interface also introduced at ESC.

Express104 specifies a 90mm x 96mm board with two 52-pin, high-speed connectors capable of supporting PCI Express and USB as well as other popular moderate speed interfaces for I/O expansion. It provides the basis for a stackable, I/O-centric, multi-board solution that is processor architecture and chipset independent.

The specification contains support for very low power and ultra mobile processors which support 'green' computing initiatives.

On a single 52-pin high-speed SUMIT-A connector, the Express104 Specification supports one x1 PCI Express lane, three high-speed USB 2.0 interfaces, low pin count bus, SPI/uWire, SMBus/I_C Bus, and ExpressCard signals.

A second identical 52-pin SUMIT-B connector supports one additional x1 PCI Express lane, one x4 PCI Express lane plus additional power, ground, and control signals.

The total number of pins is 104 for both connectors and is referred to collectively as a SUMIT Type AB configuration. Signal integrity test results demonstrate that a stack of Express104 modules will support data rates of 5 GT/s which is required for PCI Express Generation 2.

Even though Express104 modules can be constructed with only SUMIT connectors, a special configuration has been defined to support expansion with PC/104 modules. Systems conforming to the Express104 specification can then maintain legacy support for exisiting PC/104 stacking expansion I/O modules and enclosures.

The Express104 specification accomplishes this by maintaining the same placement location of the legacy PC/104 connector while also maintaining the same module physical dimensions and mounting holes.

The Small Form Factor Special Interest Group is an international organization which identifies, creates, and promotes standards to help electronics system and device manufacturers and integrators move to small form factor technologies and building blocks in their products, and protect their investments.

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