Allen-Bradley FLEX I/O 1794-IP4, Руководство пользователя, Страница: 15 / 70

1–5 Overview of the Pulse Counter Module
Publication 1794-6.5.16 – September 1998
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
Allen-Bradley HMIs