This
guide is intended to describe the use of the scanon/scanoff structure
in SPICE to produce a custom scan. The basic idea behind this
structure is that it allows any combination of drives and counts (and
other commands if required) to be converted into a custom scan.
The best way to explain this structure is by first describing the
commands which are present and then using an example.
Commands:
scanon: This command
initiates the structure. It turns on a variable which prevents
the normal output of commands, stores any errors that occur in
subsequent commands, and records the returned values of any counts that
occur.
stepend: This
command signifies the end of a step in the scan. Any counts that
have accumulated during the step are then output to the logfile and
datafile and any errors that occured are printed in the logfile on a
separate line (with the standard comment delimiter (#) in front of the
messages.
stepbegin: This
command is not required for operation of the scanon/scanoff structure
but is included for flexibility. The execution of this command
determines the point at which the motor positions will be stored for a
step. For instance, if a drive to a specific h,k,l point occured
in a step which was then followed by a drive of some motor, the user
would probably want to record motor positions after the h,k,l drive and
not after the subsequent motor drive. The use of the stepbegin
command after the drive would allow the positions to be recorded at
this point.
scanoff: This
command ends the scan and turns off the scanon variable so that normal
command execution is restored.
NOTE: if a
scanon/scanoff generated scan is stopped before execution of the scanoff
command, the program still believes that the scanon structure is
activated and will NOT
resume normal operation until a scanoff command is issured.
Examples:
The
easiest way to understand the use of this structure is through a series
of examples.
Example #1:
This example is not particularly useful but explains the basic
funtionality of the structure.
