Siemens SIMATIC MV550 S Operating Instructions Manual page 186

Service and maintenance
10.1 Error and diagnostics messages
LED Meaning
labeling
READ Green flashing:
The read result is valid.
Yellow, flashing:
The read result ended with a MATCH error.
Red, flashing:
The read result is invalid (N_OK).
186
Description and corrective measures
No error
The reading was successful and the read result is valid
(OK).
The reading was successful, but the result comparison
showed a deviation from the default (MATCH error).
The reading was unsuccessful or the read result is not valid
(N_OK).
Possible causes:
The expected codes were not in the image.
•
The processing time was not sufficient.
•
A test condition could not be fulfilled.
•
Operating Instructions, 05/2019, C79000-G8976-C494-02
SIMATIC MV500