Electronics & Embbeded Systems

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Currently the most common variety of Single Board Computer in use is of a specific form factor similar to other full-size plug-in cards and is intended to be used in a backplane. Some architectures are dependent entirely on single-board computers, such as CompactPCI, PXI, VMEbus, VXI, PICMG architecture, etc. In the Intel PC world, the intelligence and interface/control circuitry is placed on a plug-in board that is then inserted into a passive (or active) backplane. The end result is similar to having a system built with a motherboard, except that the backplane determines the slot configuration. Backplanes are available with a mix of slots (ISA, PCI, PCIX, PCI-Express, etc), usually totaling 20 or less, meaning it will fit in a 19" rackmount enclosure (17" wide chassis).

Some single-board computers also exist as form factors that stack like building blocks, and do not have the form of a traditional backplane. Examples of stacking SBC form factors include PC/104, PC/104-Plus, PCI-104, EPIC, and EBX; these systems are commonly available for use in embedded control systems.

In the Intel Single Board Computer world, PICMG provides standards for the backplane interface: PICMG 1.0, 1.1 and 1. provide for ISA and PCI support with 1.2 adding PCIX support PICMG 1. provides for PCI-Express support. Single Board Computers meeting the PICMG 1.3 specification are referred to as a System Host Board.

Stack-type SBCs often have memory provided on plug-cards such as SIMMs and DIMMs, however they can still be regarded as SBCs because although the memory modules are technically additional circuit boards, they have no extra functionality beyond providing memory and are basically just carriers for the RAM chips. Hard drive circuit boards are also not counted for determining if a computer is an SBC or not for two reasons, firstly because the HDD is regarded as a single block storage unit, and secondly because the SBC may not require a hard drive at all as most can be booted from their network connections.

Single-board computers (SBCs) are complete computers built on a single circuit board. The design is centered on a single or dual microprocessor with RAM, IO and all other features needed to be a functional computer on the one board. The first true single-board computer (see the May 1976 issue of Radio-Electronics) called the "dyna-micro" was based on the Intel C8080A, and also used Intel's first EPROM, the C1702A. The dyna-micro was re-branded by E&L Instruments of Derby, CT in 1976 as the "MMD-1" (Mini-Micro Designer 1) and was made famous as the example microcomputer in the very popular 8080 "BugBook" series of the time. SBCs also figured heavily in the early history of home computers, for example in the Acorn Electron and the BBC Micro. Other typical early single board computers were often shipped without enclosure, which had to be added by the owner, examples are the Ferguson Big Board and the Nascom.

With the development of PCs there was a sharp shift away from SBC, with computers being constructed from a motherboard, with functions like serial ports, disk drive controller and graphics being provided on daughterboards. The recent availability of advanced chip sets providing most of the I/O features as embedded components allows motherboard manufacturers to offer motherboards with I/O traditionally provided by daughterboards. Most PC motherboards now offer on-board support for disk drives including IDE and SATA with RAID, graphics, Ethernet, and traditional I/O such as serial and parallel ports, USB, and keyboard/mouse support. Plug-in cards are now more commonly high performance graphics cards (really graphic co-processors), high end RAID controllers, and specialized I/O cards such as data acquisition and DSP (Digital Signal Processor) boards.

Microcontroller Simulation Software:
Proteus VSM at http://www.labcenter.co.uk
Multisim at http://www.electronicsworkbench.com

Embedded Simulation Software:
Keil Software at http://keil.com
ASEM51
AVRSim
etc

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Microcontroller Microhip PIC Blog Community

Microcontroller AVR Blog Community