FB-354 drive incompatibility

From: Michał Pleban <lists_at_michau.name>
Date: Wed, 20 Apr 2016 13:10:59 +0200
Message-ID: <571763C3.1050803@michau.name>

I discovered an incompatibility between the FB-354B drive from A500
which I am using and FB-354C in the C65. The FB-354C has an additional
signal /DSKIN which tells the computer that the disk is inserted in the
drive. The FB-354B is missing such signal. It only has /CHNG signal,
which is supposed to be set when a disk is changed in the drive,
whatever that means. Actually I cannot figure out what this signal does,
because when I insert the disk, it always stays on whether I remove the
disk, reinsert it and so on. I don't see any way to clear it.

Right now I just hardwired /DSKIN to 0 which means the computer always
thinks there is a disk in the drive. This has an undesired side effect
that when there is no disk, any disk operation will hang because the
computer tries to spin the drive and waits for the index pulse, but the
drive refuses to spin because there is really no disk, so the index
pulse never arrives.

Obviously the FB-354B drive knows whether there is disk inserted or not,
but does not expose this information outside. Is there any way the "disk
inserted" signal could be simulated somehow based on the existing interface?


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Received on 2016-04-20 12:00:02

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