Essentials for
Beginners
This subsection discusses elementary concepts critical to rst-time
users of SCPI. Read and understand this subsection b efore going on
to another. This subsection includes the following topics:
Program and Resp onse
Messages
These paragraphs intro duce the
basic types of messages sentbetween
instruments and controllers.
Subsystem Command Trees These paragraphs describe the
tree structure used in subsystem
commands.
Subsystem Command Tables These paragraphs present the
condensed tabular format used for
documenting subsystem commands.
Reading Instrument Errors These paragraphs explain how to read
and print an instrument's internal
error messages.
Example Programs These paragraphs contain two simple
measurement programs that illustrate
basic SCPI programming principles.
Program and Response
Messages
To understand howyour instrument and controller communicate
using SCPI, you must understand the concepts of program and
response messages.
Program messages
are the formatted data sent
from the controller to the instrument. Conversely,
response messages
are the formatted data sent from the instrument to the controller.
Program messages contain one or more commands, and resp onse
messages contain one or more responses.
The controller may send commands at any time, but the instrument
sends resp onses only when sp ecically instructed to do so. The
special type of command used to instruct the instrument to send
a resp onse message is the
query
. All query mnemonics end with a
question mark. Queries return either measured values or internal
instrument settings. Anyinternal setting that can b e programmed
with SCPI can also b e queried.
Forgiving Listening and Precise Talking
SCPI uses the concept of forgiving listening and precise talking
outlined in IEEE 488.2.
Forgiving listening
means that instruments
are very exible in accepting various command and parameter
formats. For example, the swept signal generator accepts either
:POWer:STATe ON
or
:POWer:STATe 1
to turn RF output on.
Precise
talking
means that the resp onse format for a particular query is
always the same. For example, if you query the power state when it
is on (using
:POWer:STATe?
), the resp onse is always
1
, regardless of
whether you previously sent
:POWer:STATe 1
or
:POWer:STATe ON.
1-66 Getting Started Programming
To Next Page
Loading...
Need help?
General
