Siemens simatic s7-400 FM 450-1, User Manual, Page: 100 / 130

Encoder signals and their evaluation
9.5 Signal evaluation
Counter module FM 450-1
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Manual, 02/2014, A5E03648739-02
9.5 Signal evaluation
Overview
The counter module supports the count of signal edges. It usually evaluates the edge at A
(A*) (single evaluation). Options in the program of increasing the resolution:
● Single evaluation
● Double evaluation
● Quadruple evaluation
Multiple evaluation is only supported for 5-V incremental encoders which return the A and B
signal with a phase shift of 90°, for 24-V incremental 24 V encoders with a phase shift of 90°
of the A* and B* signals.
Single evaluation
In this mode, the module evaluates only one edge of signal A. Up count pulses are recorded
at the positive edge at track A, and if track B is low. Down count pulses are recorded at the
positive edge at track A, and if track B is low.
The diagram shows a single evaluation of signals:
Figure 9-4 Single evaluation