GPIB Bus Messages CMU
1100.4903.12 5.6 E-8
Interface Message
Interface messages are transferred on the data lines of the GPIB bus, the ATN control line being active.
They are used for communication between controller and instrument and can only be sent by a com-
puter which has the function of an GPIB bus controller.
Interface commands can be further subdivided into
- universal commands
- addressed commands
Universal commands act on all devices connected to the GPIB bus without previous addressing, ad-
dressed commands only act on devices previously addressed as listeners. The interface messages
relevant to the instrument are listed in Chapter 8, section Interface Messages.
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 code is used. A distinction is made according to the direction in which device mes-
sages are transferred:
Commands 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 in-
strument 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 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, re-
set and selftest.
Device-specific 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 (cf. section SCPI Introduction).
Device responses
are messages the instrument sends to the controller after a query. They can
contain measurement results, instrument settings and information on the in-
strument status (cf. section 3.5.4).
Structure and syntax of the device messages are described in the next section. In Chapter 6 all com-
mands are listed and explained in detail.
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