Siemens SIMATIC ET 200S Operating Instructions Manual page 57

The following figure illustrates the principle of continuous measurement using frequency
measurement as an example.
Figure 2-22
Gate Control
To control the 1Count24V, you have to use the gate functions.
Isochronous Mode
In isochronous mode, the 1Count24V accepts control bits and control values from the control
interface in each bus cycle and reports back the response in the same cycle.
In each cycle, the 1Count24V transfers a measured value and the status bits that were valid
at time T
The measurement starts and ends at time T
Technological Functions
Operating Instructions, 06/2010, A5E00124867-07
Principle of Continuous Measurement (Frequency Measurement Example)
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1Count24V
2.7 Measurement Modes
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