Siemens S5-135U/155U appendix STOP. The red Stop LED will then light up, Into the internal RAM

	CPUs, Memory Cards, Memory Submodules, Interface Submodules
Mode Switch	The mode switch has two settings:
RUN	In the RUN setting, the CPU 948 processes the user program when the green
	RUN LED is lit.
STOP	The CPU 948 will go to a soft STOP when you switch over from RUN to
	STOP. The red STOP LED will then light up.
Momentary-	You can initiate the Overall Reset, Reset and Restart functions with the
Contact Mode	momentary-contact mode switch and the mode changeover switch:
Switch
OVERALL RESET	Momentary-contact switch down
	During an overall reset, the internal RAM is re-initialized, i.e. existing data
	will be erased and the contents of the memory card, if present, will be copied
	into the internal RAM.
Reset	Momentary-contact switch up
	During a reset, all flags, timers, counters and the process image will be
	erased. OB 20 will be invoked. Processing of the user program will start from
	the beginning again.
Restart	Momentary-contact switch at midpoint
	With a restart, processing of the user program will continue from the point of
	interruption. The statuses of flags, timers, counters and the process image are
	retained during stoppage of the CPU.

System Manual	5-21
C79000-G8576-C199-06