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Command Reference

SCPI Basics

Chapter 4144

Command Parameters and Responses

SCPI defines different data formats for use in program and response messages. It does this to

accommodate the principle of forgiving listening and precise talking. For more information on

program data types refer to IEEE 488.2.

Forgiving listening means the command and parameter formats are flexible.

For example, with the :FREQuency:REFerence:STATe ON|OFF|1|0 command, the signal

generator accepts :FREQuency:REFerence:STATe ON, :FREQuency:REFerence:STATe 1,

:FREQ:REF:STAT ON, :FREQ:REF:STAT 1 to turn on the source’s frequency reference mode.

Each parameter type has one or more corresponding response data types. A setting that you

program using a numeric parameter returns either real or integer response data when

queried. Response data (data returned to the controller) is more concise and restricted and is

called precise talking.

Precise talking means that the response format for a particular query is always the same.

For example, if you query the power state (:POWer:ALC:STATe?) when it is on, the response is

always 1, regardless of whether you previously sent :POWer:ALC:STATe 1 or

:POWer:ALC:STATe ON.

Numeric Parameters

Numeric parameters are used in both common and subsystem commands. They accept all

commonly used decimal representations of numbers including optional signs, decimal points,

and scientific notation.

If a signal generator setting is programmed with a numeric parameter which can only assume

a finite value, it automatically rounds any entered parameter which is greater or less than the

finite value. For example, if a signal generator has a programmable output impedance of 50 or

75 ohms, and you specified 76.1 for the output impedance, the value is rounded to 75.

Table 4-3 Parameter and Response Types

Parameter Types Response Data Types

Numeric Real, Integer

Extended Numeric Real, Integer

Discrete Discrete

Boolean Numeric Boolean

String String

1 2 ... 153 154 155 156 157 158 159 160 161 162 163 ... 361 362

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