Re: How does Eject work on an Apple 3.5 drive?

[nparker@cie.uoregon.edu (Neil Parker)]

In article <1993Jan2.061850.8141@cs.uow.edu.au> david@cs.uow.edu.au (David E A Wilson) writes:
>I have looked at the IWM pinout description in tn-misc-006 and read
>descriptions of the 5.25" disk drive, Unidisk 3.5 Smartport and everything
>else I could find but have never been able to find out what the controller
>does to cause an Apple 3.5 to eject. The only additional signal the 3.5
>has over the 5.25 is the head select. How then can the drive be told to
>eject the disk?

As a previous poster noted, it's done by setting the phase lines to a weird
combination.  Here are the exact instructions:

     Get the byte at $C031.  Turn bit 6 ON, and bit 7 OFF.  Don't change
     any other bits.  Write the modified byte back to $C031.
     Turn on the drive by accessing $C0E9.
     Select the eject function by accessing $C0E1, $C0E3, and $C0E5.
     Perform the eject function by accessing $C0E7 and then $C0E6.
     When the disk is ejected (it takes about 1 second), turn the drive off
     by accessing $C0E8.
     Clear the control lines by accessing $C0E0, $C0E2, and $C0E4.
     Finally, get the byte at $C031, turn off bit 6, and write it back.

Note:  Just in case there are any typos in the above, DON'T try it with a
non-expendable disk in the drive.

The full details of this trick and many others can be obtained by anonymous
FTP from cco.caltech.edu.  Cd to /pub/apple2/info and get the file
"iwmstuff".  If you can't do anonymous FTP, I can provide copies by
e-mail.

               - Neil Parker
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