Overview Of The Startup Scenarios For S7-400-Cpus - Siemens SIMATIC S7-400 Reference Manual

2.2

Overview of the Startup Scenarios for S7-400-CPUs

Cold Restart
• At a cold restart, all the data (process image, memory markers, 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 processing is started from the beginning again (startup OB or OB 1).
Warm Restart
• At a warm restart, the process image and the non-retentive memory markers,
timers and counters are reset.
Retentive memory markers, timers and counters and all the data blocks retain
their last valid value.
• Program processing is started from the beginning again (startup OB or OB 1).
• When the power supply is interrupted, a warm restart is only possible in
backed-up mode.
Restart
• At a restart, all the data, including the process image, retain their last valid
value.
• Program processing is resumed at exactly the instruction at which the
interruption occurred.
• The outputs are not changed until the end of the current cycle.
• When the power supply is interrupted, a restart is only possible in backed-up
mode.
Automation System S7-400 CPU Specifications
A5E00165965-01
Memory Concept and Startup Scenarios
2-5