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Product Information on the Manual S7-300 Module Specifications, Edition 11/2002
A5E00213444-02
Note
A prerequisite for detecting the errors indicated by programmable diagnostic
messages is that you have assigned parameters to the digital module accordingly
in STEP 7.
Behavior upon failure of the supply voltage
The failure of the supply voltage of the SM 321; DI 16 DC 24 is always indicated
by the SF LED on the module. Furthermore, this information is made available on
the module.
The input value is initially held for 20 to 40 ms before the 0 signal is transferred to
the CPU. Supply voltage dips < 20 ms do not change the process value (see Table
4).
Triggering of the diagnostic interrupt depends on the parameter assignment (see
Section 1.4).
Failure of the supply voltage with redundant incoming supply for the sensor
supply
Note
If an external redundant source is applied simultaneously to the sensor supply
(Vs), a failure in the internal sensor supply causes a failure of the internal and/or
external sensor supply and/or a blown fuse to be indicated instead of a regular
sensor supply failure.
Short-circuit of sensor supply Vs
Irrespective of the parameter assignment, the corresponding Vs LED goes out if a
short-circuit of the sensor supply Vs occurs.
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