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User Manual 1173.9557.02 ─ 13
5.2 Messages
The messages transferred on the data lines of the GPIB bus or via the RSIB / VXI-11
protocol can be either interface messages or device messages. For a description of
interface messages refer to the relevant sections:
●
chapter 9.1.3, "GPIB Interface"
●
chapter 9.1.2, "LAN Interface"
5.2.1 Device Messages (Commands and Device Responses)
Device messages are transferred in ASCII format. 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 identifi-
cation 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 stand-
ard IEEE 488.2. Typical tasks are the management of the standardized status
registers, reset and selftest.
● Instrument-control 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.
5.2.2 SCPI Command Structure and Syntax
SCPI commands consist of a so-called header and, in most cases, one or more param-
eters. 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 mnemonics. Queries
are formed by directly appending a question mark to the header.
Common commands and device-specific commands differ in their syntax.
SCPI compatibility
Messages