Chapter 8
SCPI
Structure
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
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Implementing just standard commands on a complex communications test
system like the 4400 would lead to a poor performance. Therefore, we were
obliged to find a compromise between standard commands and performance.
This is the reason why you will find many more SCPI commands on the 4400 than
specified in the standard SCPI specification.
However, all SCPI commands implemented on the 4400 follow the standard SCPI
syntax and rules.
For additional details on the SCPI standard, the current version can be found on
page
www.scpiconsortium.org/scpistandard.htm
. You can download the full SCPI
specification from there free of charge (some 3.5 Mb in PDF format).
Structure
SCPI defines programming commands, program messages, return values and
data formats, which are consistent for all measurement systems independent of
their manufacturer and purpose.
SCPI uses a device-independent command set, the so-called
, understood by all SCPI devices.
The 4400-specific SCPI commands are called
and will only
be understood by the 4400 and its subsystems.
A subsystem in terms of SCPI is quite abstract: it is the set of commands imple-
mented to perform specific tasks of the SCPI device (the ‘measurement
subsystem’ of the 4400, for instance, is the set of commands implemented for
taking all kind of measurements, while the ‘configuration subsystem’ is the set
of all configuration commands for all areas of the 4400).
All these subsystems are using the same, SCPI-based messaging and data
formats.
Any SCPI command is built in a hierarchical way – similar to how a path in a file
system is built.
The single command elements are separated by colons (:).
The complete set of commands of a subsystem is called the ‘command tree’.
The command trees for the SCPI command set implemented on the 4400 is avail-
able in this manual.
Syntax and notation
There are two types of SCPI commands:
– compound commands and
– common commands.
Both types of commands differ in syntax.