Siemens SIMATIC S7-1200

Basic instructions
8.8 Program control operations
S7-1200 Programmable controller
310 System Manual, V4.2, 09/2016, A5E02486680-AK
Setting the PLC maximum cycle time
Configure the value for maximum scan cycle time in the Device configuration for "Cycle
time".
Table 8- 142 Cycle time values
Cycle time monitor
Minimum value
Maximum value
Default value
Maximum cycle time
1 ms
6000 ms
150 ms
Watchdog timeout
If the maximum scan cycle timer expires before the scan cycle has been completed, an error
is generated. If the user program includes a time error interrupt OB (OB 80), the CPU
executes the time error interrupt OB, which can include program logic to create a special
reaction.
If the user program does not include a time error interrupt OB, the first timeout condition is
ignored and the CPU remains in RUN mode. If a second maximum scan time timeout occurs
in the same program scan (2 times the maximum cycle time value), then an error is triggered
that causes a transition to STOP mode.
In STOP mode, your program execution stops while CPU system communications and
system diagnostics continue.
8.8.7
STP (Exit program)
Table 8- 143 STP instruction
LAD / FBD
SCL
Description
STP();
STP puts the CPU in STOP mode. When the CPU is in STOP mode, the
execution of your program and physical updates from the process image are
stopped.
For more information see: Configuring the outputs on a RUN-to-STOP transition (Page 116).
If EN = TRUE, then the CPU goes to STOP mode, the program execution stops, and the
ENO state is meaningless. Otherwise, EN = ENO = 0.