Siemens SIMATIC S7-300 FM 350-1 Manual page 132

Operating Modes, parameters and commands
7.3 Count modes
Canceling and terminating the command
When you close the software gate, counting is cancelled (canceling gate function); this
means counting begins again at the load value the next time the software gate opens.
The current count is also stored at an edge at digital input DI-Start with a closed software
gate and the count does not change.
However, counting is terminated if you close the SW gate by executing GATE_STP of
FC CNT_CTL1. DI-Start can then no longer be used to save any counter values.
Hardware interrupt on latching
A hardware interrupt may be triggered each time a counter value is saved by latching. As a
consequence, you may need to increase the interval between the edges. The hardware
interrupts will be lost if the interrupt rate is higher than the acknowledgement rate of the
system. This situation is reported by a diagnostic interrupt.
132
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01