REMOTE OPERATION
Advanced Programming
62 LDC-3900 Series
CHAPTER 3
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Since it finds it there it will be executed. If this command did not exist at this level,
the software would search down to the "TEC:" level and find and execute the
intended command, "TEC:R?".
In order to ensure the proper command is executed for the example above, the
following command string should have been issued:
"TEC:Set:R?;TEC:R?"
Once the software has "walked" to a lower path level, it remains at that level when
it receives the next command. For example, to (1) set the Laser display to show
the set point, (2) decrement the set point, and (3) set the TEC display to show the
measured temperature, the following command string could be used:
"LAS:DIS:Set;DEC;TEC:DIS:T"
When the "DEC" command is reached, the software is at the "LAS:DIS:" level.
Since there is no "DEC" command there, it walks back up to the "LAS" level, and
there it finds the "LAS:DEC" command.
The reason that the full path (including "TEC:") must be specified for the last part
(TEC:DIS:T) is that otherwise it would look for the DIS:T command in the
LAS:DIS: path, not find it, and generate error E-123.
After the second semicolon is reached (DEC;) the software will first look for the
next word (TEC) at the current path. Since it is not found it will walk back up the
tree until it finds it at the root level. Once the search walks up to the root level, it
will not walk down any other paths, unless the path is specified.
The only exception to the rule described above is when common commands are
used. In that case, the software remembers which level the user was at before the
common command was found, and it returns to that same level after finding and
executing the common command. Therefore the following command string is
legal:
"TEC:DIS:T;*WAI;DEC"
Here, (1) the display is set to show the measured temperature (2) the software
waits for the previous command to be executed, and (3) the set point is
decremented one step.
Timing Considerations
Although the shortcuts mentioned in Path Specification on page 61 reduce the
command length, they may not necessarily optimize the speed of program
execution. The following tip may be useful if speed of execution of a command is
critical. If a command follows a semicolon (;) in a command string, and it is not at
the root level, using the colon (:) will aid the software in locating the command,
and time will be saved.
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