Siemens S5-135U/155U appendix Mode Switch, STOP. The red Stop LED then lights up

CPUs, Memory Cards, Memory Submodules, Interface Submodules

Mode Switch	The mode switch has two settings:
RUN	In the RUN setting, the CPU 928-3UA21 processes the user program when
	the green RUN LED is lit.
STOP	The CPU 928-3UA21 goes to the stop state when you switch from RUN to
	STOP. The red STOP LED then lights up.
Momentary-	You can initiate the Overall Reset, Reset and Restart functions with the
Contact Mode	momentary-contact mode switch:
Switch
OVERALL RESET	Momentary-contact switch down
	With an overall reset, all RAM areas are erased and initialized.
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.

Status Indicators
	RUN	STOP	Status
	LED	LED

on

off

off

on

The CPU is in the RUN state.

The CPU is in the STOP state. After a stop request by switch or PG function, the STOP LED is continuously lit because the transition to the STOP state was requested by the user or, in multiprocessor operation, by another CPU, and was not caused by the CPU itself.

off

off

The CPU is in the INITIAL START or program check state.

off

off

slow flashing

rapid flashing

The CPU is in the STOP state. The CPU has caused a transition to the STOP state (possibly also for the other CPUs). If you set the mode switch to STOP, the flashing LED becomes continuously lit.

The CPU is in the STOP state. An overall reset has been requested. This request can be initiated by the CPU itself or by operator action.

5-58	System Manual
	C79000-G8576-C199-06