Siemens Simatic S7-400 - Manual (Page 578)

Diagnostic Data of the Signal Modules
B-4
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
B.3 Diagnostic Data of the Digital Input Modules
as of Byte 2
The structure and contents of the different bytes of the diagnostic data for special
digital input modules are described below. The following general rule applies:
When an error occurs, the bit concerned is set to ”1”.
You will find a description of possible error causes and appropriate remedies in the
section called “Diagnostics of the Modules”.
Bytes 2 and 3 of the SM 421; DI 16 24 VDC
Byte 2
7 6 0
Operating status 0: RUN
1: STOP
Module-internal supply voltage failure
5 4 3 2 1
0
Byte 3
7 6 0
EPROM error
Hardware interrupt lost
5 4 3 2 1
0
0 0 0 0 0
0 0 0 0 0
Figure B-2 Bytes 2 and 3 of the Diagnostic Data of the SM 421; DI 16 x 24 VDC