the matching command. The parameter type is listed adjacent to each named parameter.

More About Commands

Query and Event Commands. Because you can query any value that you can set, the query form of each command is not shown explicitly in the command tables. For example, the presence of the synthesizer

:SWEep : DWELl command implies that a : SWEep : DWELl? also exists. If you see a table containing a command ending with a question mark, it is a query only command. Some commands are ewe&, and cannot be queried. An event has no corresponding setting if it causes something to happen inside the instrument at a particular instant. For example, : INITiate : IMMediate causes a certain trigger sequence to initiate. Because it is an event, there is no query form of

:INITiate : IMMediate.

Implied Commands. Implied commands appear in square brackets in the command table. If you send a subcommand immediately preceding an implied command, but do not send the implied command, the instrument assumes you intend to use the implied command, and behaves just as if you had sent it. Note that this means the instrument expects you to include any parameters required by the implied command. The following example illustrates equivalent ways to program the synthesizer using explicit and implied commands.

Example synthesizer commands with and without an implied commands:

: SWEep : MANual : RELat ive 6

using

explicit

commands

:SWEep:MANual 6

using

implied

commands

Optional Parameters. Optional parameter names are enclosed in square brackets in the command table. If you do not send a value for an optional parameter, the instrument chooses a default value. The instrument’s command dictionary documents the values used for optional parameters.

Program Message Examples

The following parts of the synthesizer SCPI command set will be used to demonstrate how to create complete SCPI program messages:

:FREquency

C:CWl

:MULTiplier

: STATE

:POWER

I:: LEVEL]

Example 1: “FREQuency : CW 5 GHZ; MULTiplier 2”

1-72 Getting Started Programming