Start Period Time Measurement; Check If The Measurement Is Complete; Select Clock Frequency - Allen-Bradley FLEX I/O 1794-IP4 User Manual

4 input pulse counter module
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Allen-Bradley HMIs
Overview of the Pulse Counter Module

Start Period Time Measurement

The control bit StartMeasurement starts the measurement of the time
period.
StartMeasurement
Function
0
Period time measurement stopped (not enabled)
1
Period time measurement starts on the positive edge of the
variable

Check if the Measurement is Complete

After a complete measurement the flag MeasurementReady is set.
MeasurementReady
Function
0
The measurement is not complete
1
The positive edge of the flag indicates that the measurement is
complete
MeasurementReady is reset by the module when a positive edge of
StartMeasurement is received.

Select Clock Frequency

The clock period for the period time measurement resolution
selection can be set to 1 or 10MHz using the variable
ClockFrequency. 10MHz clock frequency is recommended at 32–bit
period time measurement to provide the best accuracy and
resolution. Use 1mHz clock frequency at 16–bit frequencies to avoid
overflow in the counter at frequencies over 15Hz.
ClockFrequency
Function
0
Clock frequency = 10MHz
1
Clock frequency = 1MHz
Publication 1794-6.5.16 – September 1998
1–5
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