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Introduction to Programming - 2Introduction to SCPISCPI (Standard Commands for Programmable Instruments) is a programming language for controllinginstrument functions over the GPIB and RS-232 interface. SCPI is layered on top of the hardware-portionof IEEE 488.2. The same SCPI commands and parameters control the same functions in differentclasses of instruments.Conventions Used in This GuideAngle brackets < > Items within angle brackets are parameter abbreviations. For example, indicates a specific form of numerical data.Vertical bar | Vertical bars separate alternative parameters. For example, NORM | TEXTindicates that either "TEXT" or "NORM" can be used as a parameter.Square Brackets [ ] Items within square brackets are optional. The representation [SOURce:].VOLTage means that SOURce: may be omitted.Braces { } Braces indicate parameters that may be repeated zero or more times. It isused especially for showing arrays. The notation {<,B>} shows thatparameter "A" must be entered, while parameter "B" may be omitted ormay be entered one or more times.Computer font Computer font is used to show program lines in text.OUTPUT 723 "TRIGger:COUNt:CURRent 10" shows a program line.Types of SCPI CommandsSCPI has two types of commands, common and subsystem.♦ Common commands generally are not related to specific operation but to controlling overallelectronic load functions, such as reset, status, and synchronization. All common commandsconsist of a three-letter mnemonic preceded by an asterisk: *RST *IDN? *SRE 8♦ Subsystem commands perform specific electronic load functions. They are organized into aninverted tree structure with the "root" at the top. The following figure shows a portion of asubsystem command tree, from which you access the commands located along the variouspaths. You can see the complete tree in Appendix A.:CURRent [:LEVel]:MODE:PROTectionROOT:DELay:STATus:CONDition?:OPERation [:EVENt]?[:LEVel][:IMMediate]Figure 2-1. Partial Command Tree17
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