Siemens Simatic S7-400 - Manual (Page 576)

Diagnostic Data of the Signal Modules
B-2
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
B.1 Evaluating the Diagnostic Data of the Signal Modules
in the User Program
In This Appendix
This Appendix describes the structure of the diagnostic data in the system data.
You must be familiar with this structure if you want to evaluate the diagnostic data
of the signal module in the STEP 7 user program.
Diagnostic Data are Contained in Data Records
The diagnostic data of a module can be up to 43 bytes long and are contained in
data records 0 and 1:
• Data record 0 contains 4 bytes of diagnostic data that describe the current
status of a programmable controller.
• Data record 1 contains the four bytes of diagnostic data that are also contained
in data record 0 and as many as 39 bytes of module-specific diagnostic data.
Further Reading
An in-depth description of the principle of evaluating the diagnostic data of signal
modules in the user program and a description of the SFCs that can be used for
that purpose will be found in the STEP 7 manuals.