SM and SUMIT-ISM Specs Bring SUMIT Expansion to 90 x 96 mm Stackable Modules

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The Small Form Factor Special Interest Group (SFF-SIG) has announced the availability of both revision 1.0 of the Industry Standard Module (ISM) and the SUMIT-ISM specifications for small, rugged, stackable embedded systems. The SUMIT-ISM specification documents the use of SFF-SIG’s flexible Stackable Unified Module Interface Technology (SUMIT) interface on popular 90 x 96 mm stackable modules. The ISM specification provides an explicit form-factor-only definition upon which the SUMIT-ISM specification is built. Since the SUMIT specification itself defines only a board-to-board interface (connectors and pin definition), the ISM specification is necessary to define the form factor while the SUMIT¬-ISM specification defines how SUMIT is implemented on ISM modules.

In order to support a wide variety of legacy 90 x 96 mm modules marketed as PC/104 or PCI-104 modules on a SUMIT-ISM stack, the SUMIT-ISM specification offers a high level of flexibility to maintain compatibility. The SUMIT-ISM specification defines two legacy stack types, using slotted mounting holes on ISM modules to provide symmetry not found with PC/104. This enables SUMIT-ISM modules to be created with legacy support for either the PC/104 ISA bus or the PCI-104 PCI bus by allowing the module to be rotated 180 degrees as necessary to fit the legacy type required while maintaining the SUMIT interface. Legacy bus support can be supplied by the CPU and maintained up the stack, or it can be provided through a bridge module in the stack itself.

With SUMIT-ISM, stackable I/O expansion is implemented using the SUMIT standard introduced by SFF-SIG in early 2008. Through the inclusion of one or two 52-pin SUMIT connectors, a SUMIT-ISM CPU can provide PCI Express (up to 6 x1 lanes or 2x1 and 1 x4 lane), USB 2.0, LPC, I2C and/or SPI interfaces to the SUMIT-ISM I/O modules. The SUMIT-ISM CPU designer has the flexibility to provide all or any subset of these interfaces.

In anticipation of the release of these specifications, SUMIT-ISM CPUs are already available from member companies ADLINK and VersaLogic. SUMIT-ISM I/O modules are available from member companies VersaLogic and WinSystems.