Testing functions, Diagnostics and Fault Elimination
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
10-9
Table 10-3 Evaluation of the SF LED (Software error)
Possible Errors Reaction of the CPU Remedies
TOD interrupt is enabled and
triggered. However, a
matching block is not
loaded.(Software/
configuration error)
OB 85 call. CPU goes
into STOP if OB 85 is
not loaded.86
Loading OB 10 or 11 (CPU 318-2
only) (OB number can be viewed in
the diagnostic buffer).
Start time of the enabled
TOD interrupt was jumped,
e.g. by advancing the
internal clock.
OB 80 call. CPU goes
into STOP if OB 80 is
not loaded.
Disable the TOD interrupt before
you set the time-of-day with
SFC29.
Delay interrupt triggered by
SFC 32. However, a
matching block is not
loaded. (Software/
configuration error)
OB 85 call. CPU goes
into STOP if OB 85 is
not loaded.
Loading OB 20 or 21 (CPU 318-2
only) (the OB number can be
viewed in the diagnostic buffer).
Process interrupt is enabled
and triggered. However, a
matching block is not
loaded. (Software/
configuration error)
OB 85 call. CPU goes
into STOP if OB 85 is
not loaded.
Loading OB 40 or 41 (CPU 318-2
only) (the OB number can be
viewed in the diagnostic buffer).
Attempt to access a missing
or faulty module. (Software
or hardware error)
OB 85 call. CPU goes
into STOP if OB85 is
not loaded or, with
loaded OB 80, if the
cycle time is
exceeded a second
time without having
been retriggered.
Generate OB 85, the start
information of the OB contains the
address of the respective module.
Replace the respective module or
eliminate the program error.
The cycle time was
exceeded. Probably too
many interrupt OBs called
simultaneously.
OB 80 call. CPU goes
into STOP when
OB 80 is not loaded or
called twice.
Extension of the cycle time
(STEP 7 – Hardware
configuration), changing the
program structure. Remedy: if
required, retrigger cycle time
monitoring via SFC 43
Programming error
• Block not loaded
• Wrong block number
• Wrong timer/counter
number
• Read/write access to
wrong area
• etc.
OB 121 call. CPU
goes into STOP if OB
121 is not loaded.
Eliminate the programming error.
The STEP 7 testing function helps
you to localize the error.
I/O access error
An error has occurred when
module data was accessed
OB 122 call. CPU
goes into STOP if OB
122 is not loaded.
Check module addressing in HW
Config or whether a module/DP
slave has failed.
Global data communication
error, e.g. insufficient length
of the DB for global data
communication.
OB 87 call. CPU goes
into STOP if OB 87 is
not loaded.
Check global data communication
in STEP 7. If required, correct the
DB size.
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