Siemens SIMATIC S7-300 FM 350-1 Manual page 150

Operating Modes, parameters and commands
7.4 Measuring modes
Edge-triggered opening and closing of the HW gate
Figure 7-36
You open the HW gate to start the measurement by setting a positive edge at digital input
DI-Start. You close the HW gate to stop the measurement by setting a positive edge at
digital input DI-Stop. The measured value which is valid at the time the HW gate is closed is
retained at the checkback interface.
If a positive edges is set in parallel at both inputs, an open gate will be closed, whereas a
closed gate remains closed. When digital input DI-Stop is set, a positive edge at digital input
DI-Start can not open the gate.
Status at the inputs DI-Start and DI-Stop
The status at inputs DI-Start and DI-Stop is returned at the green LEDs I0 and I1, and in the
user program at the STS_STA and STS_STP bits in the DB of FC CNT_CTL1.
Gate status
The gate status is indicated by the STS_GATE bit in the user program.
150
Edge-triggered opening and closing of the HW gate
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01