Siemens 6ES7521-1BL00-0AA0 Manual page 19

Meaning of the LED displays
The tables below explain the meaning of the status and error displays.
LED RUN/ERROR
Table 5- 1 RUN/ERROR status and error displays
LED
RUN ERROR
Off Off
Flashes Off
On Off
Flashes Flashes
LED CHx
Table 5- 2 CHx status display
LED CHx
Off
On
Digital input module DI 32x24VDC BA (6ES7521-1BL10-0AA0)
Manual, 12/2016, A5E32363711-AD
Meaning
Voltage missing or too low at backplane bus.
Module is starting up.
Module is ready.
Hardware defective.
Meaning
0 = Status of the input signal.
1 = Status of the input signal.
5.1 Status and error displays
Remedy
Switch on the CPU and/or the system pow-
•
er supply modules.
Verify that the U connectors are inserted.
•
Check to see if too many modules are in-
•
serted.
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Replace the module.
Remedy
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Diagnostics alarms
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