KEPCO EL Series Electronic Load Operator Manual P/N 243-1295 Firmware Version 3.63 through 3.86 - Manual (Page 49)

SERIES EL 070312
3-13
3.13.3.8 SYSTEM SUBSYSTEM
This subsystem controls various system functions.
3.13.4 PROGRAM MESSAGE STRUCTURE
SCPI program messages (commands from controller to load) consist of one or more message
units ending in a message terminator. The message terminator is not part of the syntax; it is
defined by the way your programming language indicates the end of a line: “newline” must be
defined as CR (0D
H
) followed by LF (0A
H
). The message unit is a keyword consisting of a single
command or query word followed by a message terminator (e.g., CURR? or
INPut). The message unit may include a data parameter after the keyword sepa-
rated by a space; the parameter is usually numeric (e.g., CURR 5), but may also be a
string (e.g., OUTP ON). The following subparagraphs explain each component of the
message structure.
Each command must use the full syntax shown in Appendix B. Each command must be a sepa-
rate line.
3.13.4.1 KEYWORD
Keywords are instructions recognized by a decoder within the EL Series, referred to as a
“parser.” Each keyword describes a command function; all keywords used by the EL Series are
listed in Figure 3-3.
Each keyword has a long form and a short form. For the long form the word is spelled out com-
pletely (e.g. STATUS, OUTPUT and VOLTAGE are long form keywords). For the short form only
the first three or four letters of the long form are used (e.g., STAT, OUTP and VOLT). Figure 3-3
shows the short form keywords; both short and long form keywords are found in Appendix B.
3.13.4.2 KEYWORD SEPARATOR
If a command has two or more keywords, adjacent keywords must be separated by a colon (:)
which acts as the keyword separator (e.g., SOUR:MEAS:VOLT).
3.13.4.3 QUERY INDICATOR
The question mark (?) following a keyword is a query indicator. This changes the command into
a query. If there is more than one keyword in the command, the query indicator follows the last
keyword. (e.g., VOLT? and MEAS:CURR?).
3.13.4.4 DATA
Some commands require data to accompany the keyword either in the form of a numeric value
or character string. Data always follows the last keyword of a command or query (e.g.,
SOUR:VOLT:LEV 100 or LOCK OFF.
3.13.4.4.1 MULTIPLE LINE MESSAGES
Some commands return multiple lines of data via the serial or USB port. Each line is separated
by a CR LF sequence. The GPIB and LAN interfaces change the line terminators of multiple line
messages to “CR,” (CR comma). Each line is a different data element. The longest multiple line
message contains 120,000 bytes of information (DIAG:TREE?).