Siemens Simatic S7 Series

Special memory (SM) and system symbol names
D.8 SMB6-SMB7: CPU ID, error status, and digital I/O points
S7-200 SMART
System Manual, 09/2015, A5E03822230-AC
671
D.8
SMB6-SMB7: CPU ID, error status, and digital I/O points
Special memory bytes 6 and 7 provide CPU information.
See also
SMW100-SMW114 System alarm codes (Page 684)