Siemens Simatic S7-400

Storage Concept and Startup Types
8.2 Overview of the startup scenarios for S7-400 CPUs
S7-400 Automation System, CPU Specifications
8-4 Manual, 10/2006, 6ES7498-8AA04-8BA0
8.2 Overview of the startup scenarios for S7-400 CPUs
Cold Start
● During a cold restart, all data (process image, bit memory, timers, counters and data
blocks) are reset to the start values stored in the program (load memory), irrespective of
whether they were configured as retentive or non-retentive.
● Program execution is restarted at the beginning (startup OB or OB1).
Restart (Warm Restart)
● A warm restart resets the process image and the non-retentive flags, timers, times and
counters.
Retentive flags, times and counters retain their last valid value.
All data blocks assigned the "Non Retain" attribute are reset to the load values. The
remaining data blocks retain their last valid value.
● Program execution is restarted at the beginning (startup OB or OB 1).
● After a power supply interruption, the warm restart function is only available in backup
mode.
Hot restart
● When 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.