Siemens SIMATIC S7-300 FM 350-1 Manual page 167

Double evaluation
Double evaluation refers to the evaluation of the positive and negative edges of signal A.
The logic level at signal B determines the count direction, i.e. the up or down count pulse.
The diagram shows the double evaluation of signals:
Figure 8-5
Quadruple evaluation
Quadruple evaluation refers to the evaluation of the positive and negative edges of signals A
and B. The logic level at the signals A and B determines the count direction, i.e. the up or
down count pulse.
The diagram shows quadruple evaluation of signals:
Figure 8-6
Default
Single evaluation is set by default.
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
Double evaluation
Quadruple evaluation
Encoder signals and their evaluation
8.4 Signal evaluation
167