R&S AFQ100A
Interface and Device Messages
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E-3
Device Messages (Commands and Device Responses)
Device messages are transferred on the data lines of the IEC/IEEE-bus, the "ATN" control line not
being active. ASCII character set is used.
If an Ethernet connection is present, signalling via a hardware control line is not required.
The device messages are equal for the different interfaces (IEC/IEEE bus and Ethernet). A distinction is
made according to the direction in which they are sent:
Commands
(Program
Messages)
are messages the controller sends to the instrument. They operate the device
functions and request information.
The 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 frequency.
Queries
cause data to be provided for output on the
IEC/IEEE bus, e.g. for identification of the device
or polling a parameter value. Queries are formed
by directly appending a question mark to the
header.
2. According to their definition in standard IEEE 488.2 and SCPI:
Common Commands
are exactly defined as to their function and notation
in standard IEEE 488.2. They refer to functions
such as management of the standardized status
registers, reset and selftest.
Instrument control
commands
refer to functions depending on the features of the
instrument such as frequency setting. A majority of
these commands has also been standardized by
the SCPI committee Device-specific extensions
following the SCPI rules are permitted by the
standard.
Device
responses
(
Response
Messages and
Service Request)
are messages the instrument sends to the controller after a query. They can
contain measurement results, instrument settings and information on the
instrument status (cf. section
Structure and syntax of the device messages are described in the following section.
