Siemens S7-1200 System Manual page 825

Meaning of the LED displays
The following table explains the meaning of the status and error displays. You can find
remedial measures for diagnostic alarms in the "Diagnostic alarms" section.
LED DIAG
DIAG
Off
Flashes
On
Flashes
LED port status
Valid for IO-Link port which is in IO-Link port mode.
COM/1 ... COM/4
Off
Flashes
On
LED channel status
Valid for IO-Link port which is in DI/Q mode.
DI/Q1 ... DI/Q4
Off
On
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
Meaning
Backplane bus supply of the S7-1200 not OK
Module is not configured
Module parameterized and no module diagnostics
Module parameterized and module diagnostics
OR
L+ power not connected
Meaning
Port deactivated
Port activated, device not connected or
Port is not connected to the configured device
Port activated, device connected
Meaning
Process signal = 0
Process signal = 1
SM 1278 4xIO-Link Master
15.4 Interrupt, error, and system alarms
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