Each element has a state which can be accessed via it's status dictionary.
The state is defined as a superposition of the following values:
valid - the default state of an element.
busy - indicates that this element needs more than one cycle to
update and is not yet fully updated.
updated - indicates that the element was updated in the current cycle.
once the update cycle is completed all updated flags are
changed to valid.
This flag shoulds only be set if the update cycle was
interrupted or suspended.
suspended - indicates that the update of this element was suspended. The
next call to simulate will continue with this element.
frozen - if this state is set the update cycle skips this element. In
effect the element keeps its state intact as if it was "frozen".
This is the only state which can directly be set by the user.
buffers_initialized - the buffers of the node have been initialized
err - some unspecified error condition has occured.