Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 20)

Operating and display elements
2.1 Operating and display elements: CPU 31xC
CPU 31xC and CPU 31x, Technical data
2-4
Manual, Edition 08/2004, A5E00105475-05
2.1.1 Status and Error Indicators: CPU 31xC
LED designation Color Meaning
SF red Hardware or software error
BF (for CPUs with DP
interface only)
red Bus error
DC5V green 5-V power for CPU and S7-300 bus is OK
FRCE yellow Force job is active
RUN green CPU in RUN
The LED flashes during STARTUP at a rate of 2 Hz, and in HOLD
state at 0.5 Hz.
STOP yellow CPU in STOP and HOLD or STARTUP
The LED flashes at 0.5 Hz when the CPU requests a memory reset,
and during the reset at 2 Hz.
Reference
• CPU operating modes: STEP 7 Online Help.
• Information on CPU memory reset: Operating instructions CPU 31xC and CPU31x,
Commissioning, Commissioning Modules, CPU Memory Reset by means of Mode
Selector SwitchEvaluation of the LEDs upon error or diagnostic event: Operating
Instructions CPU 31xC and CPU 31x, Test Functions, Diagnostics and Troubleshooting,
Diagnostics with the help of Status and Error LEDs