Remote Control - Fundamentals R&S
NRP
1144.1400.12 5.6
E-3
Structure and Syntax of Device-Dependent Messages
SCPI Standard
SCPI (Standard Commands for Programmable Instruments) describes a standardized command set for
the programming of instruments regardless of the type of instrument or manufacturer. The objective of
the SCPI Consortium is to standardize device-specific commands as far as possible. For this purpose, a
device model has been developed which defines identical functions within a device or between different
devices. Command systems have been created and assigned to these functions so that it is possible to
address identical functions with the same commands.
The command systems have an hierarchical structure.
Fig. 5-1
shows this tree structure, using details
from the SENSe command system which selects the measurement to be performed by the device. Most
of the other examples of command syntax and structure are taken from this command system.
SCPI is based on the IEEE 488.2 standard, i.e. it uses the same syntax elements and the common
commands defined in IEEE 488.2. The syntax of the responses is subjected to somewhat stricter rules
than those specified by the IEEE 488.2 standard (
Æ
section "
Responses to Queries
", page
5.10
).
Command Structure
Commands consist of a header and usually one or several parameters. Header and parameters are
separated by a white space (ASCII code 0 to 9, 11 to 32 decimal, e.g. space). The headers may be
composed of several keywords. The query is created by appending a question mark directly to the
header.
Common Commands
Device-independent commands consist of a header preceded by an asterisk (*) The header may be
followed by one or several parameters.
Examples:
*RST
Reset
, resets the device.
*ESE 253
Event Status Enable
, sets the bits of the Standard Event Status Enable Register.
*ESR?
Event Status Query
, queries the contents of the Standard Event Status Register.
