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SCPI Introduction

:DATA? = :data?

:SYSTem:PRESet = :system:preset

Long-Form and Short-Form Versions

A SCPI command word can be sent in its long-form or short-form version.

However, the short-form version is indicated by upper case characters.

Examples:

:SYSTem:PRESet long-form

:SYST:PRES short form

:SYSTem:PRES long-form and short-form combination

Note that each command word must be in long-form or short-form, and not

something in between.

For example, :SYSTe:PRESe is illegal and will generate an error. The

command will not be executed.

Query

Observe the following precautions with queries:

⚫ Set up the proper number of variables for the returned data. For example, if

you are reading back a measurement array, you must dimension the array

according to the number of measurements that you have placed in the

measurement buffer.

⚫ Read back all the results of a query before sending another command to the

instrument. Otherwise a Query Interrupted error will occur and the unreturned

data will be lost.

1.3 Message Type of SCPI

There are two types of SCPI messages, program and response.

⚫ Program message: A program message consists of one or more properly

formatted SCPI commands sent from the controller to the instrument. The

message, which may be sent at any time, requests the instrument to perform

some action.

⚫ Response message: A response message consists of data in a specific SCPI

format sent from the instrument to the controller. The instrument sends the

message only when commanded by a program message called a "query."

The next figure illustrates SCPI message structure:

ITech IT7900 Series Programming Guide

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