KEPCO EL Series Electronic Load Operator Manual P/N 243-1295 Firmware Version 3.12 (Unit Rev 2) - Manual (Page 48)

3-14
SERIES EL 070110
3.10.4.8 ROOT SPECIFIER
The root specifier is a colon (:) that precedes the first keyword of a program message. This
places the parser at the root (top left, Figure 3-4) of the command tree. Note the difference
between using the colon as a keyword separator and a root specifier in the following examples:
SYST:RANG:VOLT 100 Both colons are keyword separators.
:CURR:LEV:IMM 100 The first colon is the root specifier, the other two are keyword separators.
VOLT:LEV 60;:CURR:LEV 150 The second colon is the root specifier, the first and third are key-
word separators
:INP ON;:LOCK OFF;:CURR 120;VOLT:LEV 60 The first three colons are root specifiers.
3.10.4.9 MESSAGE TERMINATOR
The message terminator defines the end of a message. One message terminator is permitted:
• new line () is defined as CR (Carriage Return, 0D
H
) followed by LF (Line Feed, 0A
H
)
NOTE: The examples shown in this manual assume a message terminator will be added at the
end of each message. Where a message terminator is shown it is represented as
meaning CR (0D
H
) followed by LF (0A
H
).
3.10.5 UNDERSTANDING THE COMMAND STRUCTURE
Understanding the command structure requires an understanding of the subsystem command
tree illustrated in Figure 3-4. 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, :SENSe, :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.
3.10.6 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