Siemens SIMATIC S7-300 FM 350-1 Manual page 111

Digital Output
Parameter
Assignment
Active on reaching
the comparison value
for pulse duration
(down)*
Active on reaching
the comparison value
for pulse duration
(up/down)
DO1:
Switch to comparison
value
This deactivates DO0
* Note the boundary conditions
A shaded area in the table signifies: The output is active.
t = Pulse duration
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
Behavior of the Digital Outputs
The output is set to 1 for the period of the pulse duration when the counter
reaches the comparison value while counting up.
This requires either:
No main count direction

Main count direction up

The output is set to 1 for the period of the pulse duration when the counter
reaches the comparison value while counting down.
This requires either:
No main count direction

Main count direction down

The output is set to 1 for the period of the pulse duration, regardless of the
counting direction, when the counter reaches the comparison value while
counting down.
Requirements:
No main count direction

Output DO1 switches if the counter level lies in the range between two
comparison values.
Operating Modes, parameters and commands
7.3 Count modes
111