def registerWriteCallback(self, callback, getEnFn) -> int:
index = len(self._writeCallbacks)<EOL>self._writeCallbacks.append(None)<EOL>self._writeCallbacksToEn.append((index, callback, getEnFn))<EOL>return index<EOL>
Register writeCallback for signal.
Registration is evaluated at the end of deltastep of simulator.

:param callback: simulation process represented by function(simulator)
    which should be called after update of this signal
:param getEnFn: function() to get initial value for enable of callback