Specifications

8-164 | OWNER’S GUIDE
Miscellaneous counter functions
Filters
Each counter input has a digital lter, which can be set to various gate times. If the gate time is set to “Off”,
no lter is on the input signal. The purpose of ltering is to eliminate unstable states, e.g. glitches, chatter,et
al, which may appear on the input signal. Noise can be mis-counted, and should therefore be eliminated.
The lter circuit samples the input signal on each rising edge of the internal time base. If the input signal
maintains his state for at least the gate time, the new state is propagated. As an effect the signal transition is
shifted by the gate time.
The gure demonstrates the function of the lter:
Below, input signal with chatter, before and after ltering:
The lter can be chosen between eight lter settings:
Off, 100 ns, 200 ns, 500 ns, 1 μs, 2 μs, 4 μs and 5 μs.