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Online and diagnostic tools
14.1 Status LEDs
Description
Maintenance requested
Defective hardware
LED test or defective CPU
firmware
Unknown or incompatible
version of CPU configuration
Note
"Unknown or incompatible version of CPU configuration" error
Attempting to download an S7-1200 V3.0 program to an S7-1200 V4.0 CPU causes a CPU
error, and the CPU displays a corresponding error message in the diagnostic buffer. If you
reached this state by using an invalid version program transfer card (Page 127), then
remove the card, perform a STOP to RUN transition, a memory reset (MRES) or cycle
power. If you reach this state by an invalid program download, reset the CPU to factory
settings (Page 789). After you recover the CPU from the error condition, you can download a
valid V4.0 CPU program.
The CPU also provides two LEDs that indicate the status of the PROFINET communications.
Open the bottom terminal block cover to view the PROFINET LEDs.
● Link (green) turns on to indicate a successful connection
● Rx/Tx (yellow) turns on to indicate transmission activity
The CPU and each digital signal module (SM) provide an I/O Channel LED for each of the
digital inputs and outputs. The I/O Channel (green) turns on or off to indicate the state of the
individual input or output.
S7-1200 behavior following a fatal error
If the CPU firmware detects a fatal error it attempts a defect-mode restart, and if successful,
signals the defective mode by continually flashing the STOP/RUN, ERROR and MAINT
LEDs. The user program and hardware configuration are not loaded following the defect-
mode restart.
If the CPU successfully completes the defect-mode restart, the CPU and signal board
outputs are set to 0, and the outputs of central rack signal modules and distributed I/O are
set to the configured "Reaction to CPU STOP".
784
Forced I/O
Battery replacement
required (if battery board
installed)
STOP/RUN
Yellow / Green
On (either yellow or green)
On (yellow)
Flashing
(alternating yellow and green)
On (yellow)
ERROR
Red
-
On
Flashing
Flashing
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
MAINT
Yellow
On
Off
Flashing
Flashing
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