Siemens FM 450-1 - 5-V Differential Signals

9.3 5-V di󹪜erential signals
Count signals of 5-V incremental encoders
RS422 signals returned by the 5-V incremental encoder to the module:
• A and /A
• B and /B
• N and /N
The signals /A, /B and /N are the inverted signals of A, B and N. Signals A and B are phase-shifted
by 90°.
The tracks A and B of 5-V incremental encoders are used for counting. Track N is used to initialize
the counter with the load value, if programmed accordingly.
Encoders featuring these six signals are symmetrical encoders.
The diagram shows the time pro󹪝le of the encoder signals:
Signal A
Signal /A
Signal B
Signal /B
Signal N
Signal /N
Direction of count
Up
Down
Figure 9-1 Signals of the 5-V incremental encoder
The module detects the count direction by evaluating the ratio of signals A and B. The diagrams
in the chapter "Signal evaluation (Page 83)" show which edges of signals A and B are counted
in down or up direction.
Changing the count direction
You can change the count direction using the "Count direction normal" and "Count direction
inverted" parameters without having to modify the wiring.
Monitoring encoder signals
The module monitors the cable connection, and detects wire-break or short-circuit.
You can de󹪝ne which of the three signal pairs to include in monitoring in your program. There
is no need to wire any unused signal pairs, if you have disabled the corresponding diagnostics
functions in the program (monitoring.)
An error state at all three signals indicates a defective encoder, or a short-circuit at the "5.2 V DC"
encoder supply, or a missing encoder.
Encoder signals and their evaluation
9.3 5-V di󹪜erential signals
Counter module FM 450-1
80 Equipment Manual, 03/2022, A5E03648739-AC