Siemens SIMATIC S7-300 Manual page 17

Mode selector switch
The mode selector switch is used to set the current CPU operating mode.
Table 3-3
Position
RUN
STOP
MRES
Power supply connection
Each CPU is equipped with a double-pole power supply socket. The connector with screw
terminals is inserted into this socket when the CPU is delivered.
Status and error displays
The CPU is equipped with the following LEDs:
Table 3-4
LED
SF
BF1
BF3
5 VDC
FRCE
RUN
STOP
S7-300 CPU Data: CPU 315T-2 DP
Manual, 12/2005, A5E00427933-02
Switch positions of the mode selector switch
Meaning Description
RUN mode The CPU executes the user program.
STOP mode The CPU does not execute a user program.
CPU memory Mode selector switch position with pushbutton function for CPU
reset memory reset. A general CPU reset by means of a mode selector
switch requires a specific sequence of operation.
Status and error displays of the CPU
Color
red
red
red
green
yellow
green
yellow
Meaning
Hardware or software error
Bus errors (MPI/DP)
Bus error on DP(DRIVE)
5V power supply for the CPU and the S7-300 bus
Active force job
CPU in RUN
The LED flashes during STARTUP at a rate of 2 Hz, and in
HOLD state at 0.5 Hz.
CPU in STOP, or HOLD, or STARTUP
The LED flashes
At 0.5 Hz on general reset request
•
At 2 Hz during general reset
•
At 2 Hz during shutdown (LED RUN lit).
•
Operator controls and indicators
3-3