Siemens simatic s7-400 FM 450-1, User Manual, Page: 123 / 130

Counter module FM 450-1
Manual, 02/2014, A5E03648739-02
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Glossary
Asymmetrical signals
Refers to two pulse sequences, phase-shifted by 90°, and with zero mark signal where
applicable.
Configuration
Assignment of modules to racks, slots and addresses. Users configuring the hardware fill out
a configuration table in STEP 7.
Double evaluation
In this mode, the module evaluates all positive edges of the pulses at track A and B of an
incremental encoder.
Encoders
Encoders are used to for the precise recording of rectangular signals reflecting distances,
positions, velocity, speed, dimensions, etc.
Encoders with asymmetrical output signals
These encoders return two differential pulse sequences with 90° phase-shift, including a
zero mark signal where applicable.
Encoders with symmetrical output signals
These encoders return two differential pulse sequences with 90° phase-shift, including
inverted signals to form a zero mark as required.
Function (FC)
According to IEC 1131-3 notations, this is a code block which does not contain static data. A
function supports the transfer of parameters in a user program. Functions are thus
particularly suitable for programming complex, recurrent functions
Function module (FM)
A module which relieves the CPU of the S7 automation system of process signal processing
tasks which are critical in time or memory-intensive. As a rule, FMs use the internal
communication bus for high-speed data exchange with the CPU. Examples of FM
applications: Counting, positioning, controlling