Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 181

Error handling
Programming with foresight and, above all, knowledge and proper handling of diagnostic
tools puts you into an advantageous position in error situations:
• You can reduce the effects of errors.
• It makes it easier for you to locate errors (by programming error OBs, for example).
• You can limit downtimes.
Diagnostics with LED display
SIMATIC S7 hardware offers diagnostics with LEDs.
These LEDs are implemented in three colors:
LED color
Green
Yellow
Red
LED flashing
Two LEDs are used for Ethernet:
LED designation
LINK
RX/TX
Reference
Notes on diagnostics of I/O modules capable of diagnostics are found in the relevant
Manual.
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
Debugging functions, diagnostics and troubleshooting
Color State Meaning
Green Off No other device is connected with the integrated
PROFINET interface of the CPU.
On Another device (in most cases a switch) is connected to
the integrated PROFINET interface of the CPU, and the
physical connection is in place.
Yellow Off No activity:
No data are transferred via the integrated PROFINET
interface of the CPU.
On Activity:
Data are transferred via the integrated PROFINET
interface of the CPU.
Note: The LED flickers when small data volumes are
transferred.
10.3 Overview: Diagnostics
State of CPU
Regular operation.
Example: Power is on.
Non-regular operating status.
Example: Forcing is active.
Fault.
Example: Bus error
Special event
Example: CPU memory reset
10-5