RTC6 boards
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8 Advanced Functions for Scan Head Control and Laser Control
253
External Starts triggered by an external start
signal (or by simulate_ext_start or
simulate_ext_start_ctrl) that do not execute
immediately because of the track delay setting
are held in a queue that can accommodate up to
8 starts (each start trigger is automatically
generated when the delay has expired, see also
Section ”External Start”, page 290). This helps
avoid dead time between the execution of
multiple (Processing-on-the-fly) list programs.
Moreover, the list command simulate_ext_start
can be used to execute several lists at defined
intervals.
If wait_for_encoder, wait_for_encoder_mode,
wait_for_encoder_in_range and wait_for_mcbsp
are used to interrupt a list for intermediate
forwarding motions, see Chapter 8.6.6 ”Virtual
Image Field with Processing-on-the-fly”, page 252,
then the Signals for “Laser Active” Operation are not
changed before the forwarding motion.
With encoder-based Processing-on-the-fly
applications, the laser focus with park_position can
be moved to a safe parking position before an
interruption and back to the starting position or any
other position after an interruption with
park_return. See command description for more
details.
The behavior of the galvanometer scanners during
such a forwarding motion depends on the
Processing-on-the-fly correction used:
• With McBSP-based Processing-on-the-fly
correction as well as the encoder-based
Processing-on-the-fly corrections set_fly_x,
set_fly_y and set_fly_rot, the
galvanometer scanners are stationary relative to
the real Image Field during list interruption. As a
rule, a jump to the next marking must then be
made.
• With the encoder-based set_fly_2d
Processing-on-the-fly correction, the positions of
the galvanometer scanner are continuously
Processing-on-the-fly-corrected (the laser focus
thus remains stationary relative to the to-be-
marked object). The subsequent jump to the next
marking or continuation of the same is usually
very small.
• With set_fly_2d, clipping might occur if the
Processing-on-the-fly-corrected coordinate values
exceed the real Image Field during a long
forwarding motion. To avoid this, it might make
sense to switch off Processing-on-the-fly
correction before the forwarding motion (by
fly_return, see Chapter 8.6.5 ”Deactivating
Processing-on-the-f
ly Correction”, page 251; the
galvanometer scanners then remain stationary).
To switch correction back on after the forwarding
motion, you can use activate_fly_2d
instead of
set_fly_2d (or activate_fly_xy instead of
set_fly_x and set_fly_y). These commands do
not reset the encoders, but instead convert the
last Processing-on-the-fly-uncorrected coordinate
values such that the Processing-on-the-fly-
corrected output matches the current output.
If an error occurs when restarting with these
commands (for example, because the
recalculated coordinate values would then be
outside the 29-bit virtual Image Field, or because
another Processing-on-the-fly mode has been
activated in the meantime), then an error bit gets
set. This error bit can be read out by
get_marking_info(
Bit #9
).
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