Other signal modules
7.4 Position decoder module SM 338; POS-INPUT; (6ES7338-4BC01-0AB0)
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ
509
7.4.6 Diagnostics of SM 338; POS-INPUT
Introduction
The SM 338 provides diagnostics messages, i.e. it always provides all diagnostics messages
without user intervention.
Reactions to a diagnostic message in
STEP 7
Actions initiated by diagnostic messages:
● The diagnostic message is entered in the diagnosis of the module and forwarded to the
CPU.
● The SF LED on the module is lit.
● If you have set "Enable Diagnostic Interrupt" in
STEP 7
, the system triggers a diagnostic
interrupt and calls OB 82.
Reading diagnostic messages
You can read detailed diagnostic messages using SFCs in the user program (refer to section
Diagnostics data of SM 338; POS-INPUT (Page 596)).
You can view the cause of the error in the module diagnostics data in
STEP 7
(refer to the
STEP 7
Online Help.)
Diagnostic message using the SF LED
The SM 338 indicates errors at its SF LED (group error LED.) The
SF LED lights up when the SM 338 generates a diagnostic message. It goes dark after all
error states are cleared.
The SF LED also lights up to indicate external errors (short-circuit at the encoder supply),
regardless of the CPU operating state (at POWER ON.)
The SF LED lights up temporarily at startup, during the self test of SM 338.
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