[Coco] Mocha & OS9
robert.gault at worldnet.att.net
Wed Jan 28 08:42:15 EST 2004
Brad Grier wrote:
> I'm trying to get OS9 working in Mocha but I have a bug in the disk
> emulation. It *appears* the NMI interrupt is firing when it shouldn't
> be. My docs on the FDC are pretty sketchy - is there a flag in one of
> the registers that turns off the NMI?
> Thanks again,
Hmmm, by definition non maskable means it won't turn off. There is a
Coco flag at $982 which is used by the NMI routine. If set the routine
rti's to the address at $983, else it just does a simple rti.
The 1793 and 1773 always generate interrupts on the completion of a
task. Controllers for the Coco feed that interrupt to the NMI line.
There is no switch for this connection.
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