Siemens Simatic S7 Series

Program instructions
7.6 Counters
S7-200 SMART
218 System Manual, 09/2015, A5E03822230-AC
Example CTD count down
LAD
STL
Count down counter C1 current value
counts from 3 to 0
With I0.1 OFF, I0.0 OFF-ON decre-
ments C1 current value
I0.1 ON loads countdown preset value
3
Network 1
LD I0.0
LD I0.1
CTD C1, +3
C1 bit is ON when counter C1 current
value = 0
Network 2
LD C1
= Q0.0
Timing diagram