Siemens S7-300 Installation And Operating Manual page 304

Diagnostics data of the signal modules
A.2 Structure and Content of Diagnostic Data
Data records 0 and 1 of system data
Module diagnostics data have a maximum length of 29 bytes and are saved to data records
0 and 1 in system data:
● Data record 0 contains 4 bytes of diagnostics data which describe the status of the fail-
● Data record 1 contains
Description
The structure and content of the individual diagnostic data bytes are described below.
General rule: The corresponding bit is set to "1" if an error is detected.
Bytes 0 and 1
The diagram below shows the contents of bytes 0 and 1 in diagnostics data.
Figure A-1
304
safe signal module.
– 4 bytes of diagnostics data of the fail-safe signal module, which are also included in
data record 0,
– and up to 25 bytes of channel-specific diagnostics data
Diagnostics data bytes 0 and 1
Installation and Operating Manual, 01/2010, A5E00085586-10
Fail-safe signal modules