Siemens SIMATIC S7-400 Manual page 21

Error and Fault Displays and Special Characteristics
The three LEDs INTF, EXTF and FRCE on the front panel of the CPU indicate errors and
special features in user program execution.
Table 2-4
LED
INTF
H
x
x
x
H = LED is lit; B = LED flashes with the specified frequency; x = LED status is irrelevant
The LEDs BUS1F and BUS5F indicate errors on the MPI/DP, PROFIBUS DP and
PROFINET IO interfaces.
Table 2-5
LED
BUS1F
H
x
x
B
H = LED is lit; B = LED flashes; x = LED status is irrelevant
Error and Fault Displays and Special Characteristics
The CPUs 41x-3 also feature the IFM1F LED. This LED indicates problems relating to the
memory submodule interface.
Table 2-6
LED
IFM1F
H
B
H = LED is lit; B = LED flashes; x = LED status is irrelevant
S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0
Possible statuses of the INTF, EXTF and FRCE LEDs
Meaning
EXTF FRCE
x x An internal error was detected (programming or parameter assignment
error) or the CPU is performing a CiR.
H x An external error was detected (in other words, the cause of the error is
not on the CPU module).
x H A force job is active.
x B Node flash test function.
2 Hz
Possible states of the BUS1F and BUS5F LEDs
Meaning
BUS5F
x An error was detected on the MPI/DP interface.
x An error was detected on the PROFIBUS DP interface.
H An error was detected on the PROFINET IO interface.
x CPU is DP master:
CPU is DP slave:
Possible states of the IFM1F LED
Meaning
An error was detected on memory submodule interface.
CPU is DP master:
CPU is DP slave:
One of more slaves on the PROFIBUS DP interface
are not responding.
CPU is not addressed by the DP master.
One of more slaves on the PROFIBUS DP interface module
inserted in the receptacle are not responding.
CPU is not addressed by the DP master.
Structure of a CPU 41x
2.3 Status and error displays
2-9