KEPCO BIT 4886 Operator Manual - Manual (Page 54)

4-20
BIT 4886 120413
• carriage return (
<CR>
), ASCII 13 (decimal) or 0D (hex)
• both of the above (
<CR> <NL>
). If both are sent, the second is null and has no effect.
Your GPIB interface card software will automatically send a message terminator. For example,
the HP BASIC OUTPUT statement inserts
<NL>
after the last data byte. When binary data is
exchanged,
<END>
must be used. The combination
<NL><END>
terminator can be used for all
data except binary data.
NOTE: Kepco power modules require a message terminator at the end of each program mes-
sage. 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
<NL>
regardless of the actual terminator character.
4.6.5 UNDERSTANDING THE COMMAND STRUCTURE
Understanding the command structure requires an understanding of the subsystem command
tree illustrated in Figure 4-5. 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
omitted 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 Interface Card
are
:INITiate
,
:MEASure
,
:OUTPut
,
[:SOURce]
,
:STATus
, and
:SYSTem
. 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<NL>
The parser returns to the root due to the message terminator.
STAT:OPER?;PRES<NL>
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<NL>
After the
OPER:COND?
message unit, the parser moves in one level from
OPER
, allowing the
abbreviated notation for
STAT:OPER:ENAB
.
4.6.6 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