Re: Apple II Interrupt card

["Bill Garber" <willy46pa@comcast.net>]

Todd,
I did reply to this post, not sure what happened. It might have gone
directly
to you or just got lost or something, but I'll have to remember all I wrote
and
try again. Sorry.

Bill @ GarberStreet Enterprises
http://garberstreet.netfirms.com

Todd <tmyers@autobahn.mb.ca> wrote in message
3E7A2C04.BFDAF3D2@autobahn.mb.ca">news:3E7A2C04.BFDAF3D2@autobahn.mb.ca...
> Hi, Bill;
>
>    I've been following this thread and the parent Contiki thread (great
work, Adam!)
> and it seems that what is needed to satisfy the clock function is a
'heartbeat clock'
> that on the Apple II would be implemented via interrupts. I've taken a
look in my
> copy of the IIe tech. ref. and in slot 7 in particular is some signals
that are not
> present on any other slot. These pins deal with sub-aspects of video
signals, such as
> the colour burst @ 3.58MHz and composite sync @ 15.75KHz with 60Hz
overlaid.
>
>    That Geos Interrupt Manager card would probably get it's reference
clock from the
> Sync pin and divide it down to a usable heartbeat rate of 15Hz to 60Hz
using a divide
> by 256 to 1024 to get there. Here's a question about this, does an
interrupt routine
> need to reset the flipflop that caused the interrupt or can the circuit
for a
> heartbeat pull the interrupt for (let's say) 2 or 3 cpu clock cycles and
release it?
> If there were no other devices causing interrupts ( as in the assumed
default setup
> for a IIe with Contiki) then the only interrupt vector would be to our
heartbeat
> routine for housekeeping of the 32 bit clock. This would be a further
adaption from
> the Geos card and buildable by anyone who doesn't have one of these or
mouse cards to
> get a 60Hz heartbeat going.
>
> Later, Todd.
>
>
> Bill Garber wrote:
> >
> > > That's true. I just wonder if it's worth the cost to make a batch of
> > > interrupt manager cards, when for a few dollars more you could make
> > > something with more capability.
> > >
> > > I have also received an email from another person who thinks a simple
> > > mod to the ][ and ][+ could provide the signal necessary.
> >
> > Ok, in that case you should be able to take the signals necessary from
> > th IOU, since all the INT MGR uses, I would imagine, INT OUT, INT IN,
> > +5v, and GND. Should be fairly simple.
> >
> > Bill @ GarberStreet Enterprises
> > http://garberstreet.netfirms.com
> >
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