Instruction manual

Unsigned Compares
90
890USE18300 September 2003
Delta (∆) You can also add a ∆ value to an outside-the-window compare block, which acts as
an hysteresis around the two thresholds.
Suppose you have a window defined by TH 1 = 30 000 and TH 2 = 40 000. To that
window, you specify a ∆ of 2000. If your operational input value is less than the
TH 1 - ∆ (28 000) and is increasing in value, the result is 1. The result remains 1 until
the input value exceeds 32 000, at which point the result drops to 0. If the input value
continues to increase, the result remains at 0 until the input value reaches TH 2 + ∆
(42 000). When the input value reaches 42 000, the result rises back to 1.
If the input value is decreasing from a value greater than TH 2 + ∆ (42 000), the
reflex result is 1 until the input value reaches 38 000. At this point, the result drops
to 0 and remains there as the input value becomes less than TH 1 - ∆ (28 000). At
this point, the result rises back to 1:
While the input value is within the window defined by the threshold and the ∆, it holds
its last value.
For example, if the input value is inside the window and increasing, the result will be
0. When it exceeds 42 000, the result rises to 1. If the input value then begins to
decrease after the result has dropped, the result will remain at 1 until the input value
decreases to 38 000, at which point it will drop to 0 and will remain there until the
input value decreases to less than 28 000.
Note: To be valid, TH 2 - TH 1 must be greater than 2∆. For example, say that
TH 1 = 30 000 and TH 2 = 40 000. The ∆ value you assign to the block must
therefore be less than 5000.
1
0
65 535
32 000
0
input value
42 000
30 000 (TH 1)
1
40 000 (TH 2)
0
65 535
0
input value
38 000
28 000