Command syntax
Notice in the preceding examples that there is no colon character at the beginning of the com-
mands. A leading colon instructs the Model 2002 to interpret the command starting at the root
(highest level) of the command tree. Since the Model 2002 also starts at the root each time you
send it a new command, the leading colon is not needed (although the instrument will accept it
if you send it).
You can send multiple commands in a single message. You separate the commands with a
semicolon character. When the Model 2002 encounters a command following a semicolon, it at-
tempts to interpret the command starting at the level of the previous command, unless you pre-
cede the second command with a colon. For example, either of the following comand strings
programs the Model 2002 to the 20VDC range and uses 5VDC as a relative value (with the REF-
erence commands):
volt:dc:rang 20;ref 5;ref:stat on
volt:dc:rang 20;:volt:dc:ref 5;:volt:dc:ref:stat on
The two command strings are treated identically by the Model 2002. In the first string when
the instrument encounter
";ref 5"
, it notices the following:
• It is not the first command in the string.
• There is no leading colon on the command.
• The previous command was at the
VOLTage:DC
level.
Therefore, it interprets the command as if it were at the
VOLTage:DC
level.
3-10 IEEE-488 Bus Operation
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