Interrupts; Count Signals - Siemens SIMATIC ST-1500 Function Manual

The basics of counting, measurement and position detection
2.4 Basics of counting (digital input modules)
2.4.6

Interrupts

Hardware interrupt
The module can trigger a hardware interrupt in the CPU during operation for certain events.
The hardware interrupts can be enabled in the configuration. Refer to the device manual for
the module to learn about the events that can trigger a hardware interrupt during operation.
Note
Hardware interrupts for counting are not configurable for all digital input modules.
2.4.7 24 V count signals
24 V pulse encoder count signals
The encoder, for example an initiator (BERO) or a light barrier, returns a count signal that is
connected to the terminal (signal A) of the counter. You can also connect a signal for
direction detection (signal B).
The figure below shows an example of the time profile of the signals of a 24 V pulse encoder
with direction signal and the resulting count pulses:
Note
A signal for direction detection cannot be connected for all digital input modules.
Monitoring of encoder signals
If you enable the respective diagnostic interrupt in the device configuration, the module
triggers a diagnostic interrupt in the event of an encoder signal error.
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Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG