Debounce Module - Omega OMB-DAQBOARD-3000 Series User Manual

Trigger After Stable Mode
In the "Trigger After Stable" mode, the output of the debounce module will not change state until a period
of stability has been achieved. This means that the input has an edge and then must be stable for a period
of time equal to the debounce time.
The following time periods (T1 through T5) pertain to the above drawing. In Trigger After Stable mode,
the input signal to the debounce module is required to have a period of stability after an incoming edge, in
order for that edge to be accepted (passed through to the counter module.) The debounce time for this
example is equal to T2 and T5.
T1 – In the example above, the input signal goes high at the beginning of time period T1 but never stays
high for a period of time equal to the debounce time setting (equal to T2 for this example.)
T2 – At the end of time period T2, the input signal has transitioned high and stayed there for the required
amount of time, therefore the output transitions high. If the Input signal never stabilized in the high
state long enough, no transition would have appeared on the output and the entire disturbance on the
input would have been rejected.
T3 – During time period T3 the input signal remained steady. No change in output is seen.
T4 – During time period T4, the input signal has more disturbances and does not stabilize in any state long
enough. No change in the output is seen.
T5 – At the end of time period T5, the input signal has transitioned low and stayed there for the required
amount of time, therefore the output goes low.
Trigger Before Stable Mode
In the "Trigger Before Stable" mode, the output of the debounce module immediately changes state, but
will not change state again until a period of stability has passed. For this reason the mode can be used to
detect glitches.
The following time periods (T1 through T6) pertain to the above drawing.
T1 – In the illustrated example, the Input signal is low for the debounce time (equal to T1); therefore
when the input edge arrives at the end of time period T1 it is accepted and the Output (of the
debounce module) goes high. Note that a period of stability must precede the edge in order for the
edge to be accepted.
5-2 Counter Input Modes
Debounce Module – Trigger After Stable Mode
Debounce Module – Trigger Before Stable Mode
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DaqBoard/3000 Series User's Manual