Fluke Calibration 5730A, Operator'S Manual, Page: 142 / 260

5730A
Operators Manual
6-8
Definition: Queries and Commands
Messages directed to the 5730A Calibrator fall naturally into two categories: commands
and queries. Commands instruct the Calibrator to do something or to set a value and no
response is expected. Queries generally ask only for information from the Calibrator and
a response is always expected. Some queries also require the Calibrator to take action.
For example, the
*TST?
query has the Calibrator do a self test, then send the result to the
controller. A query always ends with a question mark. A command never ends with a
question mark. Tables 6-5 and 6-6 do not separate commands and queries. They are all
called commands and are presented together in one alphabetical list.
All query responses are generated instantly on receipt of the query. Queries generate their
output when the Calibrator executes the query rather than when the controller attempts to
read the response. The Calibrator generates the requested message and places it in an area
of memory called the output buffer. When the controller addresses the Calibrator as a
talker, the contents of the output buffer are transmitted to the controller.
Some messages have both query and command forms (for example,
*PUD
and
*PUD?
).
In such cases, the command generally sets the value of a parameter and the query
generally returns the most recent value of the parameter. Some messages are queries only
(for example,
*IDN?
). Some messages are commands only (for example,
*RST
).
Functional Elements of Commands
Table 6-1 lists the functional elements of commands described by the IEEE-488.2
standard that are used by the 5730A Calibrator. This table is for those who have a copy of
the standard and want to use it to pursue additional information. The standard provides
full definitions and syntax diagrams for each element.