Agilent Technologies N3280A manual Types of Scpi Messages, Message Unit, Channel List Parameter

4 - Introduction to Programming

Types of SCPI Messages

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

♦A program message consists of one or more properly formatted SCPI commands sent from the controller to the dc source. The message, which may be sent at any time, requests the dc source to perform some action.

♦A response message consists of data in a specific SCPI format sent from the dc source to the controller. The dc source sends the message only when commanded by a program message "query."

Figure 4-2 illustrates the SCPI message structure.

Channel

Data

Keywords

Message Unit Query Indicator

Space

VOLT : LEV 10 (@1) ; PROT ON, (@1) ; : CURR? (@1) <NL>

Keyword Separator

Message Unit Separators

Message Terminator

Root Specifier

Figure 4-2. Command Message Structure

The Message Unit

The simplest SCPI command is a single message unit consisting of a command header (or keyword) followed by a message terminator. The message unit may include a parameter after the header. The parameter can be numeric or a string.

ABORt<NL>

VOLTage 20<NL>

Channel List Parameter

The channel parameter is required to address one or more channels. It has the following syntax: (@<channel> [,<channel>][,<channel>][,<channel>])

You can also specify a range of sequential channels using the following syntax: <start_channel> : <end_channel>

For example, (@2) specifies channel 2 and (@1:3) specifies channels 1 through 3. The Agilent N3280A only supports channels 1 through 4. A maximum of 4 channels may be specified through a combination of single channels and ranges. Query and measurement channel lists are order-sensitive. Results are returned in the order they are specified in the list.

NOTE: When adding a channel list parameter to a query, you must include a space (white space) between the query indicator (?) and the channel list parameter. Otherwise error –103, Invalid separator will occur

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