Startup Mode - Siemens SIMATIC CPU 410 System Manual

Memory reset
The memory reset function affects only the selected CPU. To reset both CPUs, you must
reset one and then the other.
7.1.3

STARTUP mode

Startup types
The CPU 410 distinguishes between two startup types: cold restart and warm restart.
Cold restart
● During a cold restart, all data (process image, bit memory, timers, counters and data
blocks) is reset to the start values stored in the program (load memory), regardless of
whether they were configured as retentive or non-retentive.
● The associated startup OB is OB 102
● Program execution is restarted from the beginning (OB 102 or OB 1).
Warm restart
● A warm restart resets the process image and the bit memories, timers, and counters.
All data blocks assigned the "Non Retain" attribute are reset to the start values from the
load memory.
The other data blocks retain their last valid value if buffering is active. If there is no
buffering, the values are reset to the start values from the load memory after power
off/on.
● The associated startup OB is OB 100
● Program execution is restarted from the beginning (OB 100 or OB 1).
Special features in redundant mode
The special features described below apply to startup when you operate two CPUs 410
redundantly.
Startup processing by the master CPU
The startup system state is always processed by the master CPU in redundant mode.
During STARTUP, the master CPU compares the existing I/O configuration with the
hardware configuration that you created in STEP 7. If these are different, the system can
only be started up if "Startup when expected/actual configurations differ" was configured.
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC
System and operating states of the CPU 410
7.1 CPU 410 operating modes
103