What is the difference between warm start, cold start and hot start in Siemens PLC CPU? -Solutions - Huaqiang Electronic Network

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Warm start, cold start, hot start in Siemens plc CPU, what is the essential difference between them? What is the real use in practical applications?
A: Coldstart: All data (process image, bit memory, timers and counters) are initialized, including the data blocks are reset to the initial values ​​stored in the load memory (Loadmemory), and these Whether the data is configured to be maintained or not is irrelevant. The startup organization block OB102 is executed first, and not all CPUs of the S7400 support this function.
Warmrestart: Reset process image (PII, PIQ) and non-retentive bit memory (M), timer (T) and counter (C). The defined retentive memory (M), timer (T) and counter (C) will retain their last valid value. When there is a backup battery, all DB block data is saved. When there is no backup battery, DB data and M, T, and C cannot be maintained because there is no non-volatile memory area. This is the biggest difference between 300 and S7-400 PLC.
The startup organization block OB100 is executed first. If the user has not changed the startup type, the system defaults to a warm restart.
Manual warm start: STOP->RUN (select warm start in CPU property, if CPU has CRST/WRST selector switch, it must be set to CRST to perform manual warm start)
Automatic warm start: PowerOff->PowerOn (that is, the automatic warm start will be performed when the CPU is powered on, and the CRST/WRST selector switch has no effect on it)
Hotstart: This is only possible if there is a backup battery, and all data will retain its last valid value. The program executes from the breakpoint and the output does not change its state until the current loop is completed. OB101 is executed at startup.
Only the S7-400CPU can be warm-started.
Manual hot start: STOP->RUN+WRST (Select hot start in CPU attribute, if CPU has CRST/WRST selection switch, it must be set to WRST to perform manual hot start)
Automatic hot start: PowerOff->PowerOn (hot start is to perform automatic hot start when the CPU is powered on, CRST / WRST select switch has no effect on it)