Technical data

Optional Command Keywords
Some layers in the SCPI command structure are optional. These optional keywords
are indicated by square brackets ([]). A typical use for these types of keywords is
with a command that is unique to one module. In this case, the top layer (Root
Keyword) of the command structure may be omitted.
For example, the following command code segments are functionally identical:
[SOURce[1]:]PATTern:MDENsity[:DENSity] <NR3>
SOURce:PATTERN:MDENSITY <NR3>
PATTern:MDENsity <NR3>
PATT:MDEN <NR3>
patt:mden <NR3>
Note that it is not necessary to include the syntax inside the square brackets ([]).
Sending Commands
Commands are sent over the GPIB in the same way that GPIB and IEEE 488.2
common commands are sent. The difference is that the SCPI command is "nested"
into the programming language of choice. The programming language of choice
may be a language such as Visual Basic, C++, or SICL.
For an examples of how commands are sent, see “Sending Commands to the Serial
BERT - Concepts” on page 86.
Query Responses
It is possible to interrogate the individual settings and status of a device using
query commands. Retrieving data is a two-stage operation.
The query command is sent from the controller using the OUTPUT statement and
the data is read from the device using the ENTER statement. A typical example,
using the SCPI IEEE 488.2 Common Command *IDN? which queries the identity of
a device.
See “Sending Commands using VISA” on page 87 for an example in the C
programming language of how to query the identity.
N O T E
When sending strings to the instrument, either the double quote (") or the single
quote may be used ('), the latter being more suited to PASCAL programs, which
make use of a single quote; the former being more suited to use in BASIC programs,
which use a double quote as a delimiter. In this manual, the double quote has been
used throughout.
4 SCPI Command Language
84 Agilent J-BERT N4903B High-Performance Serial BERT