Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 209

Structure of the interrupt data when a diagnostic interrupt is generated in response to an operating
status change by the intelligent slave (after byte y+4)
Byte y+1 contains the code for a diagnostic interrupt (01
16 bytes of status information from the CPU. The figure below shows the allocation of the
first four bytes of diagnostic data. The next 12 bytes are always 0.
The data in these bytes correspond to the contents of data record 0 of diagnostic data in
STEP 7 (in this case, not all bits are used).
Byte y+4
Byte y+5
Byte y+6
Byte y+7
Note: Byte y+8 to byte y+19 are always 0.
Figure 10-6
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
7 6 5 4 3 2 1 0 Bit no.
0 0 0 0 0 0 0
0: module OK
1: module error
7 6 5 4 3 2 1 0 Bit no.
0 0 0 0 1 0 1 1
ID for address areas of intermediate
memory (constant)
7 6 5 4 3 2 1 0 Bit no.
0 0 0 0 0 0 0
0: RUN mode
1: STOP mode
7 6 5 4 3 2 1 0 Bit no.
0 0 0 0 0 0 0 0
Bytes y+4 to y+7 for a diagnostic interrupt (operating status change by intelligent slave)
Debugging functions, diagnostics and troubleshooting
). The diagnostic data contains the
H
10.7 Diagnostics of DP CPUs
10-33