Siemens SIMATIC ST-1500 Function Manual page 48

2.2 Basics of counting, measuring and position input (TM Count, TM PosInput, Compact CPU)
Setting by the user program up to comparison value
You can set the respective digital output to 1 (edge) by setting the control bit (Page 185)
SET_DQm. The respective digital output is set to 0 by any of the following events:
● Match of the counter value and the comparison value in the configured direction of the
comparison event
● Reset of the corresponding SET_DQm control bit.
The figure below shows an example of the comparison event when counting in an upwards
direction:
You can disable the digital output before the counter value reaches the comparison value by
setting the control bit SET_DQm to 0.
Note
If the comparison value is reached in the configured count direction, the feedback bit
EVENT_CMPm is set independently of the state of the control bit SET_DQm.
The comparison event switches a digital output when a count pulse reaches the respective
comparison value. The digital output does not switch when the counter value is set, by
synchronization for example.
Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG
The basics of counting, measurement and position detection
47