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FASTBUS (IEEE 960) is a computer bus standard, originally intended to replace CAMAC in high-speed, large-scale data acquisition. It is also a modular crate electronics standard commonly used in data acquisition systems in particle physics experiments. == Bus Description == A FASTBUS system consists of one or more segments. Each segment may be a "crate segment" or a "cable segment". Segments are connected together using a segment interconnect (SI). A crate segment typically consists of a backplane with slots to hold up to 25 modules, mounted in a 19-inch rack. Each module is typically a printed circuit board with a front panel, similar to a Blade PC. Modules are physically about 14 inches by 15 inches, and may occupy one or more adjacent slots.〔 Small systems may consist of only one crate segment, or a small number of independent crate segments connected directly to a central computer rather than using segment interconnects. FASTBUS uses the Emitter coupled logic (ECL) electrical standard, which allows higher speed than TTL and generates less switching noise. Segments implement a 32-bit multiplexed address/data bus, which allows a larger address space than CAMAC. A module may be a Master or slave. There may be multiple masters in a segment; masters arbitrate for control of the bus and then perform data transfers to or from slaves. This allows for very fast read-out of an entire segment by doing a chained block read from a master with a general-purpose CPU. Each IO card will then assume mastership, send its data and then hand off mastership to the next card in a sequence, all without the overhead of the supervising board with the general-purpose CPU. Cable Segments are implemented using 32-bit-wide parallel twisted-pair cables and a differential signalling scheme. The electrical standard allows regular ECL receiver chips but requires custom transmitter circuits which allow lines to be safely driven both high and low at the same time - this feature is required by the arbitration logic. Full-size crates hold 26 modules.〔(【引用サイトリンク】url=http://www-esd.fnal.gov/esd/catalog/intro/introfb.htm )〕 Each module may dissipate up to 70 W, giving a total crate heat load of 1750 W. Modules require a −5.2 V supply for the ECL interface, usually a separate −2 V supply for ECL termination, and often a +5V supply for TTL or CMOS logic. The fastbus standard also has +15V and -15V pins on the backplane, which are typically fed with very small power supplies as most modules use very little +/- 15V (or any at all). Special high-capacity power supplies with large 15V supplie would have to be used if modules drew large amounts of current on those rails. Crates typically have dedicated 200 A or 300 A switched-mode power supplies, providing current to the modules through multiple pins on the backplane connector. A large installation typically has multiple racks, each with three crates. Cooling and air handling are a significant issue, as is the safe design of high-current power distribution. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「FASTBUS」の詳細全文を読む スポンサード リンク
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