KEPCO EL Series Electronic Load Operator Manual P/N 243-1295 Firmware Version 3.22 through 3.41 - Manual (Page 49)

SERIES EL 062011
3-15
3.13.5 UNDERSTANDING THE COMMAND STRUCTURE
Understanding the command structure requires an understanding of the subsystem command
tree illustrated in Figure 3-3. 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 electronic load 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 EL Series
are :MEASure,
:INPut, :OUTPut, [:SOURce], :PROTection, :STATus, and :SYSTem. Because the [SOURce]
keyword is optional, the parser moves the path to the next level, so that VOLTage, CURRent,
and MEASure 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, CHANnel, and QUEStionable.
A command must contain the short form (the part of the command in capital letters in appendix
B) or the full command. Commands and values are not case sensitive.
Command strings must be sent as a single message at all times. it is possible to send multiple
command/query strings by separating the commands with a CR. If multiple commands and/or
queries are sent this way, each response must be separated by a CR.
Commands that change a setting must be preceded or followed by a query. This response must
be accepted by the host prior to sending a new command. Example: volt 10\rvolt?\r\n changes
the voltage setpoint of the EL load (\r is CR and \n is NL).
3.13.6 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.
• UPPER case letters in mnemonics are mandatory (short form). Lower case letters may
either be omitted, or must be specified completely (long form)
e.g., PROTection (long form) has the same effect as PROT (short form).
• Commands/queries may be given in upper/lower case (long form)
e.g., SoUrCe is allowed.
• Text shown between brackets [ ] is optional.
e.g., :[SOUR:]VOLT[:LEV][:AMPL]? has the same effect as :VOLT?