Siemens S5-155U System Manual page 161

Mode switch
RUN
STOP
Momentary-contact mode
switch
OVERALL RESET
RESET
Restart
System Manual
C79000-B8576-C199-03
The mode switch has two settings:
In the RUN setting, the CPU 948 processes the user program when the
green RUN LED is lit.
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.
You can initiate the Overall Reset, Reset and Restart functions with
the momentary-contact mode switch and the mode changeover switch:
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.
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.
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.
CPU 948
5
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