Siemens SIMATIC ET 200S Operating Instructions Manual page 165

The following figure illustrates the principle of continuous measurement using frequency
measurement as an example.
Figure 3-23
Gate Control
To control the 1Count5V/500kHz, you have to use the gate functions.
Isochrone Mode
In isochrone mode, the 1Count5V/500kHz 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 1Count5V/500kHz transfers a measured value and the status bits that
were valid at the time T
The measurement starts and ends at time T
Technological Functions
Operating Instructions, 02/2007, A5E00124867-05
Principle of Continuous Measurement (Frequency Measurement Example)
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1Count5V/500kHz
3.7 Measurement Modes
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