Date   : Tue, 17 Jan 1984 12:56:29 PST
From   : Willard Korfhage <korfhage@ucla-ats>
Subject: Function 37 - disk door open

   Floppy disk controller chips can check for an open door by monitoring
the sector hole sensor (the 1791 does this). If the chip doesn't receive
a pulse from the sensor within xx milliseconds of the last pulse, then it
knows the disk has stopped rotating, presumably because the door has been
opened. If I read the data sheet properly, the 1791 can send an interrupt
when this happens.
   This technique, of course, works for any floppy, regardless of size.

               Willard Korfhage