Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 440 / 813

Remote Control: Introduction R&S
®
ZVA/ZVB/ZVT
1145.1084.12 5.8 E-1
Device Messages (Commands and Device Responses)
Device messages are transferred via the data lines of the GPIB bus, the "ATN" control line not being
active. The ASCII character set is used. A distinction is made according to the direction in which device
messages are transferred:
•
Commands are messages the controller sends to the instrument. They operate the device
functions and request information.
•
Device responses are messages the instrument sends to the controller after a query. They can
contain measurement results, instrument settings and information on the instrument status.
Commands are subdivided according to two criteria:
1. According to the effect they have on the instrument:
•
Setting commands cause instrument settings such as a reset of the instrument or setting the
output level to some value.
•
Queries cause data to be provided for output on the GPIB bus, e.g. for identification of the
device or polling the active input.
2. According to their definition in standard IEEE 488.2:
•
Common commands have a function and syntax that is exactly defined in standard IEEE 488.2.
Typical tasks are the management of the standardized status registers, reset and selftest.
•
Device-specific commands are functions that depend on the features of the instrument such as
frequency settings. A majority of these commands has also been standardized by the SCPI
consortium.
The device messages have a characteristic structure and syntax. In the SCPI reference chapter all
commands are listed and explained in detail.
SCPI Command Structure and Syntax
SCPI commands consist of a so-called header and, in most cases, one or more parameters. The
header and the parameters are separated by a "white space" (ASCII code 0 to 9, 11 to 32 decimal, e.g.
blank). The headers may consist of several key words. Queries are formed by directly appending a
question mark to the header.
Common commands and device-specific commands differ in their syntax.
Common Commands
Common (=device-independent) commands consist of a header preceded by an asterisk "*" and
possibly one or more parameters.
Examples:
*RST RESET, resets the instrument.
*ESE 253 EVENT STATUS ENABLE, sets the bits of the event status enable registers.
*ESR? EVENT STATUS QUERY, queries the contents of the event status register.