Overview of Messages

The information that is exchanged between the controller (computer) and the device (PMX series) is called a message.

The PMX uses the SCPI language for the messages.

There are two types of messages: commands that are sent from the computer to the PMX; responses that are sent from the PMX to the computer.

Command Hierarchy

SCPI commands are ASCII-based commands designed for test and measurement devices. The command hierarchy is structured around the common root or node, which is the construction block of the SCPI subsystem. A command consists of a program header, parameters, and punctuation.

The hierarchy is explained using the SOURce subsystem as an example.

 

Program header Parameter Hierarchy of node
SOUR:   Root node
  CURR Second level
  :EXT Third level
  :SOUR <bool> Fourth level
VOLT Second level
  [:PROT] Third level
  [:LEV] <numeric> Fourth level

 

A higher node is separated from a lower node using a colon (:).

Command Syntax

This manual denotes SCPI commands using the following format.

[SOURce:]CURRent[:LEVel][:IMMediate][:AMPLitude] {<numeric>|MINimum|MAXimum}

SCPI commands can be issued using the short form. The short form of a SCPI command is the section of the command written in uppercase.

SCPI commands can be sent in the long form or short form. Since SCPI commands are not case-sensitive, CURR, Curr, and curr are all accepted as the short form of CURRent. In the long form, CURRENT, Current, and current are all acceptable.

• A space is required between the program header section and the parameter section.

• Multiple parameters, when available, are concatenated using commas.

• Commands are concatenated using semicolons (compound command).

SOURce:CURRent MINimum;VOLTage MINimum

In the second command, SOURce is omitted. This is because the path is set to SOURce by the first command SOURce:CURRent MINimum.

This compound command is the same as entering the following commands.

SOURce:CURRent MINimum

SOURce:VOLTage MINimum

An error occurs if a node that is not defined in the current path is designated.

Commands of different subsystems can be concatenated using a colon and a semicolon together.

SOURce:CURRent MINimum;:MEASure:CURRent?

This compound command contains two root nodes, SOURce and MEASure.

When the second or subsequent command starts with a colon, the path specified by the previous command is cleared.

• The maximum number of characters that can be transmitted in a single line is 128.

Special symbols

Special symbols used in this manual to describe SCPI commands are defined below. Note that these symbols need to be excluded from the commands your programming.

• Characters and numbers delimited by "|" in braces indicate that one of the items is to be selected.

Do not write the braces in the actual program.

• The characters <> indicate program data.

Do not write <> in the actual program.

• Brackets indicate option data.

When option data is not sent with the program, the default value is applied.
Do not write [ ] in the actual program.

Queries

The device settings or status can be queried.

To make a query, add a question mark at the end of the program header section.

When you enter a query with parameters, add a space between the question mark and the parameter.

SOURce:CURRent? MIN

Response

A response is an answer returned in response to a query. It is a message that is always sent from the device to the computer. A response communicates such information as the status of a device or the measured values.

NOTE

When transmitting two queries in separate lines, complete reading the response to the first query before transmitting the second line. If you send two lines of query commands at once, an incomplete response may be received.

Program terminator

All commands must be terminated using a valid terminator.

The available terminators are <new line> (ASCII 0x0A) and EOI (end-or-identify). Either one can be used as a terminator.

EOI cannot be used with the RS232C interface. Be sure to use <new line>.

When a command string is terminated, the path is reset to the root level.

NOTE

CR (ASCII 0x0D) is not a terminator.

Common commands

The IEEE-488.2 and SCPI standards contain a set of common commands for reset, self-test, and other functions. These common commands always start with an asterisk. The commands may have one or multiple parameters.

>top