Siemens S5-135U/155U System Manual page 161

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
C79000-G8576-C199-06
CPUs, Memory Cards, Memory Submodules, Interface Submodules
5-21