Monitoring Functions Of The Cpu - Siemens SIMATIC S7-400 Reference Manual

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Monitoring Functions of the CPU

Monitoring and Error Messages
The CPU hardware and the operating system have monitoring functions that
ensure that the system functions correctly and that there is a defined response in
the event of an error. A number of errors will also produce a response from the
user program.
The following table gives you an overview of possible errors, their causes and the
responses of the CPU.
Type of
Fault/Error
Clock pulse Monitoring of the failure of the processor
failure clock pulse
System standstill
Access error Module failure (SM, FM, CP)
Clock Start a program synchronized to the
synchronous DP clock
interrupt
•
Timing error The runtime of the user program (OB1
and all the interrupts and error OBs)
exceeds the specified maximum cycle
time.
•
OB request error
•
Overrun of the start information buffer
•
Time error interrupt
•
Re-enter RUN following CiR
Power supply In the central or distributed I/O rack:
•
module error
At least one backup battery in the
(not power
power supply module is empty.
•
failure)
The backup voltage is missing.
•
The 24 V supply to the power supply
module has failed.
Diagnostic An I/O module with interrupt capability
Interrupt reports a diagnostic interrupt.
Remove/insert Removal or insertion of an SM and
interrupt insertion of an incorrect module type. The
LED EXTF will not light up if the only
inserted SM is removed from the CPU in
STOP during default configuration. The
LED lights up briefly when the SM is
inserted again.
Automation System S7-400 CPU Specifications
A5E00165965-01
Cause of Fault
Structure of a CPU 41x
Response of the Operating
System
Disabling of the digital outputs by
issuing the "OD" (Output Disable)
signal
"EXTF" LED lights up until the fault is
acknowledged.
In SMs:
•
OB 122 call
•
Entry in the diagnostic 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:
•
OB 122 call
Call OB 61 to OB 64
"INTF" LED lights up until the fault is
acknowledged.
OB 80 call
If the OB is not loaded: The CPU
goes into STOP mode.
OB 81 call
If the OB is not loaded: The CPU
continues to run.
OB 82 call
If the OB is not loaded: The CPU
goes into STOP mode.
OB 83 call
If the OB is not loaded: The CPU
goes into STOP mode.
Error LED
–
EXTF
–
INTF
EXTF
EXTF
EXTF
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