Rs422 Count Signals - Siemens SIMATIC ST-1500 Function Manual

2.2 Basics of counting, measuring and position input (TM Count, TM PosInput, Compact CPU)
2.2.13.2

RS422 count signals

RS422 incremental encoder count signals
The RS422 incremental encoder sends the following differential signals to the technology
module:
● A and /A
● B and /B
● N and /N
The signal information for RS422 signals is encoded in the differential voltage between A
and /A, B and /B or N and /N. The A and B signals are phase-shifted by 90°. You can also
connect incremental encoders without an N signal.
RS422 incremental encoders use the A and B signals for counting. If configured accordingly,
the N signal is used for setting the counter to the start value or for saving the current counter
value as the Capture value.
The figure below shows an example of the time profile of the signals of an RS422
incremental encoder:
The technology module detects the count direction by evaluating the sequence of edges of
the A and B signals. You can specify an inversion of the count direction.
Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG
The basics of counting, measurement and position detection
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