Siemens S7-300 appendix Status and Error Indicators CPU 31xC, LED designation Color Meaning

Operating and display elements

2.1 Operating and display elements: CPU 31xC

2.1.1Status and Error Indicators: CPU 31xC

LED designation	Color	Meaning
SF	red	Hardware or software error
BF (for CPUs with DP	red	Bus error
interface only)
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

2-4	CPU 31xC and CPU 31x, Technical data
	Manual, Edition 08/2004, A5E00105475-05