SET_IRQ_HANDLER
SET_IRQ_HANDLER( fd_rwsec_done );
SET_IRQ_HANDLER( NULL );
SET_IRQ_HANDLER( fd_writetrack_done );
SET_IRQ_HANDLER( NULL );
SET_IRQ_HANDLER( finish_fdc_done );
SET_IRQ_HANDLER( fd_calibrate_done );
SET_IRQ_HANDLER( fd_seek_done );