Monitoring Functions Of The Cpu - Siemens SIMATIC S7-400H System Manual

Installation of a CPU 41x–H

5.2 Monitoring functions of the CPU

5.2 Monitoring functions of the CPU
Monitoring functions and error messages
The hardware and operating system of the CPU provide monitoring functions to ensure
proper operation and defined reactions to errors. Various errors may also trigger a reaction
in the user program.
The table below provides an overview of possible errors and their causes, and the
corresponding reactions of the CPU.
Additional testing and information functions are available on each CPU and can be called in
STEP 7.
Error class Cause of error
Access error Module failure (SM, FM, CP)
Timeout error •
•
•
•
Power supply In the central or expansion rack:
module(s) fault
•
(not line power
failure)
•
•
Diagnostic An I/O module which supports interrupts
interrupt reports a diagnostics interrupt.
Removal/insertion Removal or insertion of an SM, and insertion
interrupt of a wrong module type.
CPU hardware •
fault
•
44
The user program execution time (OB 1
and all interrupt and error OBs) exceeds
the specified maximum cycle time.
OB request error
Overflow of the start information buffer
Time-of-day error interrupt
at least one backup battery in the power
supply module is flat.
the backup voltage is missing.
the 24 V supply to the power supply
module has failed.
A memory error was detected and
eliminated
Redundant link: Data transfer errors.
Reaction of the operating system
LED "EXTF" remains lit until the error
is eliminated.
In SMs:
Call of OB 122
•
Entry in the diagnostics buffer
•
In the case of input modules: Entry
•
of "null" for the date in the
accumulator or the process image
In the case of other modules:
Call of OB 122
•
LED "INTF" remains lit until the error is
eliminated.
Call of OB 80.
If the OB is not loaded: CPU goes into
STOP mode.
Call of OB 81
If the OB is not loaded: The CPU
remains in RUN.
Call of OB 82
If the OB is not loaded: CPU goes into
STOP mode.
Call of OB 83
If the OB is not loaded: CPU goes into
STOP mode.
Call of OB 84
If the OB is not loaded: The CPU
remains in RUN.
System Manual, 09/2007, A5E00267695-03
Error LED
EXTF
INTF
EXTF
EXTF
EXTF
INTF
S7-400H