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Simulation Limitations
Realtime vs. Neartime
Some systematic limitations are set by the speed at which Lingo, the
scripting language used by Macromedia Director,
executes commands in the compiled Director movie. CPU time is a critical
factor and forces certain limitations that are not limitations of a real
oscilloscope:
Trigger functions are only exectued neartime, and Lissajous figures need
a while to show-up if the horizontal frequency is higher than the vertical
frequency (in that case only the first "typical" image is drawn as otherwise,
to obtain the closed curve, the image needed to be rotated with each new
sample processed).
Realtime triggering is impossible, too. The triggerlevel of the
autotrigger can be set to "manual" using the "At/Norm."
switch and adjusted using the level adjuster,
but the buttons
"Trig.", "TV
Sep."
and "Ext." have no function.
Both channels are triggered at the same time.
When 10x zoom (X-Mag.)
is turned on and long Time/Div.
settings are used, the number of samples is reduced on purpose greatly, so
that the curve looks coarse. In long Time/Div. settings the beam movement is
simulated close-to-reality only, too, a realtime-simulatioin is impossible.
Computer Uptime must be less than 25 Days
During tests on a server that is up continuously it has been observed
that mask positions of long "Time/Div."
settings are not processed properly. Timing of mask movements is bound to
the computer uptime of the machine the simulation is run on, because a
reference time is needed to manage timing services. Unfortunately, the
simulation does not work error-free on computers that have been up approx.
25 days or longer before the simulation is started. The reason for it is,
that the Director Software measures the time from computer start on in ms
and uses it as a reference value. The biggest number that can be counted by
Director is approx. 2.1 billion. 25 days equal about 2.1 billion ms. If
between the start of the computer and the sart of the simulation in the
webbrowser 25 days or more have passed, timing of mask positions cannot be
calculated correctly anymore, as Director does not allow numbers of the
dimension needed. So the masks do not move at all. This behavior has been
verified using suitable tests, the reason is definitely right, but it is yet
unclear, if the error can be worked around and if, how this could be done.
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