Capture (Latch); Capture With Incremental Or Pulse Encoder - Siemens SIMATIC ST-1500 Function Manual

The basics of counting, measurement and position detection
2.2 Basics of counting, measuring and position input (TM Count, TM PosInput, Compact CPU)
2.2.6

Capture (Latch)

2.2.6.1

Capture with incremental or pulse encoder

Description
The "Capture" function is used to save the current counter value with an external reference
signal. You can configure the Capture function for the following reference signals:
● Rising or falling edge at a digital input
● Rising and falling edge at a digital input
● Rising edge of signal N at the encoder input
Function principle
The Capture value is always the exact counter value at the time of the edge in question
(delayed by the configured input filter time). The Capture function is effective regardless of
the status of the internal gate. The unchanged counter value is saved when the gate is
closed.
The figure below shows an example of the Capture function with the following configuration:
● Start value = 0
● Capture event upon rising edge at configured digital input
● Set counter to start value at gate start
● Continue counting after Capture event
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Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG