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 system on a chip (SoC). The devices integrated in the SoM typically requires a high level of interconnection for reasons such as speed, timing, bus width, etc. 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. Two other major advantages of SoMs are design-reuse and that they can be integrated into many embedded computer applications.^{[further explanation needed]}

The acronym SoM has its roots in the blade-based modules. In the mid 1980s, when VMEbus blades used M-Modules,^[1] these were commonly referred to as system On a module (SoM).^{[citation needed]} These SoMs performed specific functions such as compute functions and data acquisition functions. SoMs were used extensively by Sun Microsystems, Motorola, Xerox, DEC, and IBM in their blade computers.

A typical SoM consists of:

• at least one microcontroller, microprocessor or digital signal processor (DSP) core
  • multiprocessor systems-on-chip (MPSoCs) have more than one processor core
• memory blocks including a selection of ROM, RAM, EEPROM and/or flash memory
• timing sources
• industry standard communication interfaces such as USB, FireWire, Ethernet, USART, SPI, I²C
• peripherals including counter-timers, real-time timers and power-on reset generators
• analog interfaces including analog-to-digital converters and digital-to-analog converters
• voltage regulators and power management circuits

• CompactPCI – Computer bus interconnect for industrial computers
• Futurebus – Universal computer bus standard
• PCI Mezzanine Card – Printed circuit board assembly manufactured to the IEEE P1386.1 standard
• VPX – Standards for connecting components of a computer
• VXS – VMEbus performance improvement standard