Parallel SCSI: Difference between revisions

Revision as of 03:10, 25 October 2021

Revision as of 17:09, 27 November 2021

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===Ultra-640===

Ultra-640 (otherwise known as '''Fast-320''') was promulgated as a standard (INCITS 367-2003 or SPI-5) in early 2003. It doubles the interface speed yet again, this time to 640&nbsp;MB/s. Ultra-640 pushes the limits of LVD signaling; the speed limits cable lengths drastically, making it impractical for more than one or two devices. Because of this, manufacturers skipped over Ultra-640 and developed for [[Serial Attached SCSI]] instead.<!--[[User:Kvng/RTH]]-->

==SCSI signals==

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{{notelist-ua|refs=<ref name="Phase">These 3 signals are driven by a target during information transfer to indicate the [[#Bus Phaseoperation|bus phase]].</ref>}}

There are also three DC-level signals:

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|GROUND||Most spare pins in the connector are designated as grounds

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There are three electrically different variants of the SCSI parallel bus: [[Single-ended signalling|single-ended]] (SE), high-voltage differential (HVD), and low-voltage differential (LVD). The HVD and LVD versions use [[differential signaling]] and so they require a pair of wires for each signal. So the number of signals required to implement a SCSI bus is a function of the bus width and voltage:

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|16-bit||4-bit||16

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==Bus operation==