KEPCO KLP Series Developers Guide, Rev 3 - Manual (Page 87)

KLP-DEV 041213
6-7
6.6 UNDERSTANDING THE COMMAND STRUCTURE
Understanding the command structure requires an understanding of the subsystem command
tree illustrated in Figure 6-2. The “root” is located at the top left corner of the diagram. The
parser goes to the root if:
• a message terminator is recognized by the parser
• a root specifier is recognized by the parser
Optional keywords are enclosed in brackets [ ] for identification; optional keywords can be omit-
ted and the power supply will respond as if they were included in the message. The root level
keyword [SOURce] is an optional keyword. Starting at the root, there are various branches or
paths corresponding to the subsystems. The root keywords for the KLP Power Supply are
:ABORt, :CALibrate, :DISPlay, :LIST, :MEASure, :OUTPut, [:SOURce], :STATus, :STORage,
:SYSTem and :TRIGger. Because the [SOURce] keyword is optional, the parser moves the path
to the next level, so that VOLTage, CURRent, and FUNCtion commands are at the root level.
Each time the parser encounters a keyword separator, the parser moves to the next indented
level of the tree diagram. As an example, the STATus branch is a root level branch that has
three sub-branches: OPERation, PRESet, and QUEStionable. The following illustrates how
SCPI code is interpreted by the parser:
STAT:PRES
The parser returns to the root due to the message terminator.
STAT:OPER?;PRES
The parser moves one level in from STAT. The next command is expected at the level defined
by the colon in front of OPER?. Thus you can combine the following message units
STAT:OPER? and STAT:PRES;
STAT:OPER:COND?;ENAB 16
After the OPER:COND? message unit, the parser moves in one level from OPER, allowing the
abbreviated notation for STAT:OPER:ENAB.
6.7 PROGRAM MESSAGE SYNTAX SUMMARY
• Common commands begin with an asterisk (*).
• Queries end with a question mark (?).
• Program messages consist of a root keyword and, in some cases, one or more message
units separated by a colon (:) followed by a message terminator. Several message units
of a program message may be separated by a semicolon (;) without repeating the root
keyword.
• If a program message has more than one message unit, then a colon (:) must precede
the next keyword in order to set the parser back to the root (otherwise the next keyword
will be taken as a subunit of the previous message unit).
e.g., the command meas:volt?;curr? will read output voltage and output current
since both volt? and curr? are interpreted as subunits of the meas command.