Siemens SIMATIC S7-300 FM 350-1 Manual page 116

Operating Modes, parameters and commands
7.3 Count modes
Behavior of the Digital Outputs in Isochronous Mode
In isochronous mode, the outputs DO0 and DO1 switch immediately after the comparison
conditions are fulfilled, and are thus independent of the PROFIBUS DP cycle.
Exception:
If you have set the behavior of the digital outputs to "inactive" and, after enabling with
CTRL_DO0 or CTRL_DO1, you activate the outputs with the control signal SET_DO0 or
SET_DO1, the outputs are set and reset at the time T
116
.
o
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01