Parts of a scpi message – Agilent Technologies 664xA User Manual
Page 11
Remote Programming 11
Figure 2-1. Command Message Structure
The basic parts of the message in Figure 2-1 are:
Message Component
Example
Headers
VOLT LEV PROT CURR
Header Separator
The colon in VOLT:LEV
Data
4.5 4.8
Data Separator
The space in VOLT 4. 5 and PROT 4. 8
Message Units
VOLT:LEV 4.5 PROT 4.8 CURR?
Message Unit Separator
The semicolons in VOLT: LEV 4. 5; and PROT 4. 8;
Root Specifier
The colon in PROT 4. 8; : CURR?
Query Indicator
The question mark in CURR?
Message Terminator
The <NL> (newline) indicator. Terminators are not part of the SCPI syntax.
Parts of a SCPI Message
Headers
Headers (which are sometimes known as "keywords") are instructions recognized by the power supply interface. Headers
may be either in the long form or the short form.
Long Form
The header is completely spelled out, such as VOLTAGE STATUS DELAY.
Short Form
The header has only the first three or four letters, such as VOLT STAT DEL.
Short form headers are constructed according to the following rules:
•
If the header consists of four or fewer letters, use all the letters. (DFI DATA)
•
If the header consists of five or more letters and the fourth letter is not a vowel (a,e,i,o,u), use the first four
letters. (VOLTage STATus)
•
If the header consists of five or more letters and the fourth letter is a vowel (a,e,i,o,u), use the first three letters.
(DELay CLEar)
You must follow the above rules when entering headers. Creating an arbitrary form, such as QUEST for QUESTIONABLE,
will result in an error. The SCPI interface is not sensitive to case. It will recognize any case mixture, such as VOLTAGE,
Voltage, Volt, volt.
Note
Shortform headers result in faster program execution.