System on module
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A system on a module (SOM) is a board-level circuit that integrates a system function in a single module. It may integrate digital and analog functions on a single board. A typical application is in the area of embedded systems. Unlike a Single Board computer, a SOM serves a special function like a SoC. The device integrated in the SOM typically requires a high level of interconnection for reasons such as speed, timing, bus-width etc., in a highly integrated module. There are benefits in building a SOM, as for SoC, one notable result is to reduce the cost of the base board or the main PCB. A major advantage of SOM is design-reuse and that it can be integrated into many embedded computer applications.
This acronym SOM has its roots in the Blade based modules. In the mid 80's, when VME blades used daughter/Mezzanine modules, these were commonly referred to as System On a Module (SOM). These SOM's performed specific functions such as Compute functions and Data acquisition functions. SOM's were and still are extensively used by SUN Microsystems, Motorola, Xerox, DEC, and IBM in their Blade computers.
A typical SOM consists of:
- a microcontroller, microprocessor or digital signal processor (DSP) core – multiprocessor SoCs (MPSoC) have more than one processor core
- memory blocks including a selection of ROM, RAM, EEPROM and/or flash memory
- timing sources
- industry standards interface such as USB, FireWire, Ethernet, USART, SPI
- peripherals including counter-timers, real-time timers and power-on reset generators
- analog interfaces including ADCs and DACs
- voltage regulators and power management circuits
- ANSI/IEEE Std 1014-1987 and ANSI/VITA 1-1994
- 1386-2001 - IEEE Standard for a Common Mezzanine Card Family: CMC
- Standard ANSI/VITA 46.0-2007