Special Signal modules
5-17
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
5.4.10 Diagnosis of the SM 338; POS-INPUT
The SM 338 makes diagnostic messages available, i.e., all diagnostic messages
are always provided by the SM 338 without your assistance.
Actions following diagnostic message in STEP 7
Each diagnostic message leads to the following actions:
• The diagnostic message is entered in the diagnosis of the module and
forwarded to the CPU.
• The SF LED on the module lights.
• If you have programmed “Enable Diagnostic Interrupt” in STEP 7 , a diagnostic
interrupt is triggered and OB 82 is called.
Reading out diagnostic messages
You can read out detailed diagnostic messages by means of SFCs in the user
program (refer to the Appendix “Diagnostic Data of Signal Modules”).
You can view the cause of the error in STEP 7, in the module diagnosis (refer to
online Help for STEP 7).
Diagnostic message via SF LED
The SM 338 indicate errors for you by means of their SF LED (group error LED).
The SF LED lights as soon as a diagnostic message is triggered by the SM 338. It
goes out when all errors have been rectified.
The group fault (SF) LED also lights up in case of external errors (short circuit of
encoder supply), independent of the operating status of the CPU (if power is on).
The SF LED lights up temporarily at startup during the self test of the SM 338.
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