Siemens SIMATIC S7-400 Reference Manual page 418

Diagnostic data of signal modules
B.4 Diagnostic data of the digital output modules as of byte 2
Bytes 4 to 8 of the SM 422; DO 16 x AC 20-120 V/2 A
Table B-16
Byte 4
Byte 5
Byte 6
Byte 7
418
Bytes 4 to 8 of the diagnostic data of the SM 422; DO 16 x AC 20-120 V/2 A
Byte Bit
7 0
6 Channel type B#16#72: digital output
5
4
3
2
1
0
7 Number of diagnostics bits that the module outputs per channel: 8 bits long
0
7 Number of channels of the same type in one module: 16 channels
0
7 Channel error 7
6 Channel error 6
5 ...
4 ...
3 ...
2 ...
1 Channel error 1
0 Channel error 0
Meaning
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08