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S5-115U Manual
5
Error Diagnostics
Malfunctions in the S5-115U can have various causes. If the PLC malfunctions, first determine
whether the problem is in the CPU, the program, or the I/O modules (see Table 5-1).
Fault/Error Condition
The CPU is in the "STOP"
mode.
The red LED is lit up.
The CPU is in the "RUN"
mode.
The green LED is lit up.
Operation is faulty.
Note
To make a general distinction between PLC and program errors, program OB1 with
"BE" as the first statement. A properly functioning PLC enters the "RUN" mode on a
Cold Restart.
Caution
!
There are risks involved in changing the internal program memory direct with the
DISPLAY DIR programmer function.
For example, if the CPU is in RUN mode, memory areas (e.g. BSTACK) may be over-
written causing the CPU to "crash".
Take the following measures to avoid such risks:
•
Change only the system data area documented in this manual
•
Use only the control program to change the system data area!
EWA 4NEB 811 6130-02b
Table 5-1. General Error Analysis
Fault/Error Analysis
The problem is in the CPU.
Perform an interrupt analysis with the programmer
(see Section 5-1).
There is a program error. Determine the error address
(see Section 5-2).
There is an I/O problem. Perform a malfunction analysis
(see Section 5-3).
Error Diagnostics
5-1
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