Standard Commands for Programmable Instruments: Difference between revisions

Revision as of 23:54, 18 November 2024

Revision as of 00:10, 19 November 2024

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SCPI was defined as an additional layer on top of the {{nowrap|IEEE 488.2-1987}} specification "Standard Codes, Formats, Protocols, and Common Commands".<ref>[http://zone.ni.com/devzone/cda/tut/p/id/3419 ni.com - History of GPIB - Developer Zone]</ref> The standard specifies a common [[syntax]], [[command (computing)|command]] structure, and [[Data type|data format]]s, to be used with all instruments. It introduced generic commands (such as <code>CONFigure</code> and <code>MEASure</code>) that could be used with any instrument. These commands are grouped into subsystems. SCPI also defines several classes of instruments. For example, any controllable [[power supply]] would implement the same <code>DCPSUPPLY</code> base functionality class. Instrument classes specify which subsystems they implement, as well as any instrument-specific features.

The physical hardware communications link (physical layer) is not defined by SCPI.<ref name="IVI-SCPI"/> While it was originally created for the [[IEEE-488]].1 (GPIB) bus,<ref name="IVI-SCPI"/> SCPI can also be used with [[RS-232]], [[RS-422]], [[RS-485]], [[Universal Serial Bus|USB]], [[Ethernet]], [[VME eXtensions for Instrumentation|VXIbus]], [[HiSLIP]], etc.<ref name="IVI-SCPI">{{cite web |title=The SCPI Standard (overview) |url=https://www.ivifoundation.org/About-IVI/scpi.html |website=IVI Foundation |archive-url=https://web.archive.org/web/20240921020849/https://www.ivifoundation.org/About-IVI/scpi.html |archive-date=September 21, 2024 |url-status=live}}</ref>

SCPI commands are [[ASCII]] textual strings,<ref name="IVI-SCPI"/> which are sent to the instrument over the physical layer (e.g.,<ref IEEEname="IVI-488.1).SCPI"/> Commands are a series of one or more keywords, many of which take parameters. In the specification, keywords are written <code>CONFigure</CODE>: The entire keyword can be used, or it can be abbreviated to just the uppercase portion. Responses to query commands are typically ASCII strings. However, for bulk data, binary formats can be used.<ref name="SCPI-1999-spec"/>

The SCPI specification consists of four volumes: Volume 1: "Syntax and Style", Volume 2: "Command Reference", Volume 3: "Data Interchange Format", Volume 4: "Instrument Classes".<ref name="SCPI-1999-spec"/> The specification was originally released as non-free printed manuals, then later as aone free [[PDF]] file that includes all four volumes.

===SCPI history===