Usage: int ddu_set_dd_wait(dd_wait);
Returns: 0 if good status, -1 if bad status.
dd_wait DD_WAIT_SLEEP process falls asleep if no eventNote that ddu_set_dd_wait can be called at any time. This allows a process to switch back and forth between different modes. The default value is as specified in ddu_init.available
DD_WAIT_ASYNC process returns with nonzero (positive) status word
if no event available.