9 Introduction to SCPI
SCPI (Standard Commands for Programmable Instruments) is a programming language for
controlling instrument functions over the RS232 or IEEE 488 bus. The same SCPI
commands and parameters control the same functions in different classes of instruments.
For example, you would use the same MEAS:VOLT? command to measure the AC source
output voltage or the output voltage of a SCPI-compatible Multimeter.
9.1 Conventions Used in This Manual
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, 0 | 1
indicates that either "0" or "1" can be used as a parameter.
Square Brackets[] Items within square brackets are optional. The representation
[SOURce:]VOLT means that SOURce: may be omitted.
Boldface font Boldface font is used to emphasize syntax in command definitions.
CURR <NRf> shows a command definition.
Upper case font Upper case font is used to show program lines in text. OUTP 1
shows a program line.
9.2 The SCPI Commands and Messages
This paragraph explains the syntax difference between SCPI Commands and SCPI
messages.
The AC source supports two types of commands, IEEE-488-2 common and SCPI
subsystem.
IEEE-488-2 common commands are generally not related to specific operations but to
controlling overall AC source functions such as reset, status and synchronization. All
common commands consist of a three-letter mnemonic preceded by an asterisk:
*RST *IDN? *SRE 255
SCPI subsystem commands perform specific AC source functions. They are organized
into an inverted tree structure with the "root" at the top. Some are single commands
while others are grouped within specific subsystems. You must include the root
header in all commands sent to the AC source.
Refer to appendix A for the AC source SCPI tree structure.
Types of SCPI Messages
There are two types of SCPI messages, program and response.
A program message consists of one or more properly formatted SCPI commands sent
from the controller to the AC source. The message, which may be sent at any time,
requests the AC source to perform some action.
A response message consists of data in a specific SCPI format sent from the AC source
to the controller. The AC source sends the message only when commanded by a
program message called a "query."
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