R&S NRP2, User Manual

Page: 191 / 437

Remote Control Fundamentals
R&S
®
NRP2
173 User Manual 1173.9157.02 ─ 03
5.6.2.2 Responses
Responses are messages sent by the device to the controller after a query. This may be
measurement results, for instance, or device status information.
5.7 Structure and Syntax of device-dependent Messages
5.7.1 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. The
​
SCPI command tree ,
​
figure 5-1 shows this tree structure, using
details from the
SENSe
command system which selects the measurement to be per-
formed 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 syn-
tax of the responses is subjected to somewhat stricter rules than those specified by the
IEEE 488.2 standard (
​
chapter 5.7.4, "Responses to Queries" , on page 177).
5.7.2 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.
5.7.2.1 Common Commands
Device-independent commands consist of a header preceded by an asterisk (*). The
header may be followed by one or several parameters.
Example:
*RST RESET Resets the instrument.
*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.
Structure and Syntax of device-dependent Messages