A More Flexible DIT Engine
2 Apr 2004
Until few day ago, the Fasti way to program the detector
effective integration time (named DIT or TINT) was minimal. We
waere able to program DIT with a granularity of .1s up to 22s
ant with a 1s granularity up to 220s. No longer integration
times were available.
Now we implemented a 3 nested delay loops of delay. The
granularity of inner delay is 4ms. The delay is now performed
using a three level delay loop. This nested loops structure
requires three integer numbers, each less than 255, with a
total product equal the desired time, each unit worth 4ms. Of
course is not always possible to get such a decomposition. We
have written a mathematical procedure which tries to get the
decomposition for the number requested, and, if this is not
possible, add or subtract a small correction until find a
suitable triplet of factors.
This approach then can generate delay times which can contain
small errors. We have tested all possibilities up to 5000s (the
maximum DIT programmable is 125000s). The relative error is
plotted in the next figure.
Relative error up to 5000s
Next figure show an enlarged view of the 1-60s area, were we get the larger errors.
The higest error value (0.4% of error) is at at a time of 28.1s, not a probable one.
Relative error up to 60s
Last figure show an enlarged view of the 1-600s area, but only for integer
values of DIT. The error values are sensibly less (at most 0.08% of error).
Relative error up to 600s for integer values