Commissioning
6-10 AutomationSystem S7-400 Hardwareand Installation
A5E00850741-01
6.6 Cold, Warm, and Hot Restarts with the Mode SelectorSwitch

Restart (warm start)

•A restart resets the process image and the non--retentiveflags, timers, times
and counters.
Retentive flags, times and counters retain their last valid value.
All DBs assigned the “Non Retain” attribute are reset to load values. The
remaining DBs retain their last valid value.
•Program execution is restarted at the start position (startup OB or OB 1).
•After a power supply interruption, the warm restart function is only available in
backup mode.

Hot restart

•Wihen a hot restart is performed, all data and the process image retain their last
valid value.
•Program execution is resumed at the breakpoint.
•The outputs do not change their status until the current cycle is completed.
•After a power supply interruption, the hot restart function is only available in
backup mode.

Control sequence for restart (warm restart) / hot restart

1. Setthe switch to STOP.
Result: The STOP LED is lit.
2. Setthe switch to RUN.
Whether the CPU executes a restart / hot restart depends on the CPU
configuration.