Technical description
3 Supporting functions
3.9 Self-supervision
VM265.EN011
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3.9.
Self-supervision
The functions of the micro controller and the associated
circuitry, as well as the program execution are supervised by
means of a separate watchdog circuit. Besides supervising the
relay, the watchdog circuit attempts to restart the micro
controller in a fault situation. If the restarting fails, the
watchdog issues a self-supervision alarm indicating a
permanent internal fault.
When the watchdog circuit detects a permanent fault, it always
blocks any control of other output relays (except for the self-
supervision output relay).
In addition, the internal supply voltages are supervised. Should
the auxiliary supply of the relay disappear, an alarm is
automatically given because the internal fault (IF) output relay
functions on a working current principle. This means that the
IF relay is energized when the auxiliary supply is on and no
internal fault is detected.
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