4 - Introduction to Programming
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Introduction to SCPI
SCPI (Standard Commands for Programmable Instruments) is a programming language for controlling
instrument functions over the GPIB. SCPI is layered on top of the hardware-portion of IEEE 488.2. The
same SCPI commands and parameters control the same functions in different classes of instruments.
Conventions Used in This Guide
Angle brackets < > Items within angle brackets are parameter abbreviations. For example, <NR1>
indicates a specific form of numerical data.
Vertical bar | Vertical bars separate alternative parameters. For example, VOLT | CURR
indicates that either "VOLT" or "CURR" 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 is used
especially for showing arrays. The notation <A>{<,B>} shows that parameter "A"
must be entered, while parameter "B" may be omitted or may be entered one or
more times.
Parentheses ( ) Items within parentheses are used in place of the usual parameter types to specify a
channel list. The notation (@1:3) specifies a channel list that includes channels 1,
2, and 3. The notation (@1,3) specifies a channel list that includes only channels 1
and 3.
Computer font Computer font is used to show program lines in text.
TRIGger:ACQuire:SOURce BUS shows a program line.
Types of SCPI Commands
SCPI has two types of commands, common and subsystem.
♦ Common commands generally are not related to specific operation but to controlling overall dc
source functions, such as reset, status, and synchronization. All common commands consist of a
three-letter mnemonic preceded by an asterisk: *RST *IDN? *SRE 8
♦ Subsystem commands perform specific dc source functions. They are organized into an inverted tree
structure with the "root" at the top. The following figure shows a portion of a subsystem command
tree, from which you access the commands located along the various paths. You can see the complete
tree in Appendix. D.
:OUTPut [:STATe]
:OSCProtect
:PROTection
ROOT
:CLEar
:STATus
:CONDition?
:OPERation [:EVEN]?
[:STATe]
Figure 4-1. Partial Command Tree