Siemens S7-400 Cold, Warm, and Hot Restarts with the Mode Selector Switch, Restart warm start

Commissioning

6.6Cold, Warm, and Hot Restarts with the Mode Selector Switch

Restart (warm start)

•A 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 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.Set the switch to STOP. Result: The STOP LED is lit.

2.Set the switch to RUN.

Whether the CPU executes a restart / hot restart depends on the CPU configuration.

6-10	Automation System S7-400	Hardware and Installation
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