Siemens Simatic M7-400 Reference Manual page 131

4.4 Diagnostics of the Digital Modules
Programmable and Non-Programmable Diagnostic Messages
In diagnostics, we make a distinction between programmable and
non-programmable diagnostic messages.
You obtain programmable diagnostic messages only if you have enabled
diagnostics by parameter assignment. You perform parameter assignment in the
"Diagnostics" parameter block in STEP 7 (refer to Section 5.7).
Non-programmable diagnostic messages are always made available by the digital
module irrespective of diagnostics being enabled.
Actions Following Diagnostic Message in STEP 7
Each diagnostic message leads to the following actions:
• 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 parameterized "Enable Diagnostic Interrupt" in STEP 7, a diagnostic
interrupt is triggered and OB 82 is called (refer to Section 4.5).
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 the STEP 7 online help system).
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 technical specifications of the modules, starting at Section 4.7, to find
out which digital modules have these fault LEDs.
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Digital Modules
4-9