Diagnostic Options With Step 7 - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

• Reading a data record with SFC 59 "RD_REC"
• Reading out the start information of the current OB, using SFC 6 "RD_SINFO"
10.4

Diagnostic options with STEP 7

Diagnostics with the "Hardware Diagnostics" function
Locate the cause of a module error by viewing the online information on the module. You
can locate the cause of an error in the user program cycle with the help of the diagnostic
buffer and of the stack content. You can also check whether a user program will run on a
specific CPU.
Hardware diagnostics give you an overview of the PLC status. In an overview
representation, a symbol can display the error status of every module. A double-click on the
faulty module opens detailed error information. The scope of this information depends on the
specific module. You can view the following information:
• Display of general information on the module (e.g. order No., version, designation) and
• Indication of module errors (channel error, for example) at local I/O and PROFIBUS DP
• Display of messages from the diagnostic buffer.
• In addition, diagnostics data about the PROFINET interface are presented.
For CPUs you can also view the following module status information:
• Cause of an error in the user program cycle.
• Indication of the cycle time (longest, shortest and last cycle).
• Options and utilization of MPI communication.
• Indication of performance data (number of possible I/O, memory bits, counters, timers
For details on diagnostic functions in STEP 7 and on procedures, refer to the
with STEP 7
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
You can use SFC 59 "RD_REC" (read record) to read a specific data record from the
addressed module. Data records 0 and 1 are especially suitable for reading diagnostic
information from a diagnosable module.
Data record 0 contains 4 bytes of diagnostic data describing the current state of a signal
module. Data record 1 contains the 4 bytes of diagnostic data also stored in data record
0, plus module-specific diagnostic data.
Error information is also found in the start information of the relevant error OB.
You can use SFC 6 "RD_SINFO" (read start information) to read the start information of
the OB that was last called and not yet processed completely, and of the start-up OB that
was last called.
module status (e.g. error).
slaves or PROFINET IO devices.
and blocks).
Manual and to the
Debugging functions, diagnostics and troubleshooting
HW Config Online Help
10.4 Diagnostic options with STEP 7
Programming
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10-7