Siemens SIMATIC S7-300 FM 350-1 Manual page 131

Function principle
The counter and latch values are assigned a start value.
The count function starts when the SW gate has opened. The counter starts at the load
value.
The latch value is always equivalent to the counter value at the time the edge trigger is
generated.
The status at input DI-Start is indicated at the STS_STA status bit in the DB.
The latch value is indicated at LATCH_LOAD in the DB.
Figure 7-28
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
Latch when load value = 0 and positive edge at input DI-Start
Operating Modes, parameters and commands
7.3 Count modes
131