Internal Gate - 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)
Edge-triggered opening and closing of the hardware gate with two digital inputs
The figure below shows an example of opening and closing with two digital inputs. The two
digital inputs are configured so that the rising edge of the hardware gate opens:
The hardware gate is opened with the configured edge at the digital input that is configured
for opening. The hardware gate is closed with the configured edge at the digital input that is
configured for closing.
2.2.5.3

Internal gate

Internal gate
The internal gate is open if the software gate is open and the hardware gate is open or has
not been configured. The status of the internal gate is indicated by the feedback bit
(Page 188) STS_GATE.
If the internal gate is open, counting is started. If the internal gate is closed, all other count
pulses are ignored and counting is stopped.
If you want to control a counting process with the hardware gate only, the software gate must
be open. If you do not configure a hardware gate, the hardware gate is considered to be
always open. In this case, you open and close the internal gate with the software gate only.
Hardware gate
Open/not configured
Open/not configured
closed
closed
When you configure the counter behavior, you can specify whether the counting process is
to start from the start value or from the current counter value when the internal gate is
opened.
The internal gate can also be automatically closed upon violation of a counting limit. The
software or hardware gate must then be closed and reopened to continue counting.
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Software gate
open
closed
open
closed
Internal gate
open
closed
closed
closed
Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG