Siemens SIMATIC S7-400 Reference Manual page 89

You only obtain programmable diagnostic messages if you have enabled the diagnostics using
the relevant parameters. You perform parameter assignment in the "Diagnostics" tab in
7 , see section 6.7.
Digital modules always return non-programmable diagnostic messages, irrespective of
diagnostics being enabled.
Reactions to diagnostic messages in STEP 7
Actions initiated by diagnostic messages:
● The diagnostic message is entered in the diagnostics of the digital module, forwarded to
the CPU and can be read out by the user program.
● The fault LED on the digital module lights up.
● If you have set "Enable diagnostic interrupt" in
and OB 82 is called, see section 5.5.
Reading diagnostic messages
You can read detailed diagnostic messages using SFCs in the user program (refer to the
appendix "Diagnostic data of signal modules").
You can view the cause of the error in
help for STEP 7 ).
Diagnostics using the INTF and EXTF LEDs
Some digital modules indicate faults by means of their two fault LEDs INTF (internal fault) and
EXTF (external fault). The LEDs go out when all the internal and external faults have been
eliminated.
Refer to the specifications of the modules beginning with section 5.7 to find out which digital
modules have these fault LEDs.
See also
General information about parameter assignment (Page 199)
Interrupts of the digital modules (Page 93)
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
4.4 Diagnostics for digital modules
STEP 7 , a diagnostic interrupt is triggered
STEP 7 in the module diagnostics (refer to the online
Digital modules
STEP
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