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Re: Uthernet II manual updated, probe algorithm corrected

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On Saturday, 9 January 2016 18:07:22 UTC-8, David Empson  wrote:
> David Schmenk <dschmenk@gmail.com> wrote:
> 
> > On Saturday, 9 January 2016 13:35:47 UTC-8, D Finnigan  wrote:
> > > David Schmenk wrote:
> > > > 
> > > > David-
> > > > 
> > > > I read the pointer first and see if it gets incremented by a read instead
> > > > of assuming it starts at zero. Seems to work well for me.
> > > 
> > > Thanks for the suggestion. How much of a concern do you think it is to be
> > > blindly poking at the $C0 space? In other words, do you have personal
> > > experience or anecdotal evidence that other peripherals may be affected?
> > 
> > Well, there is always a chance it could mess something up. Reading is
> > usually somewhat benign - you may clear a status bit or something.
> 
> There are many cards where merely reading a soft switch will do
> something to it. Off the top of my head:
> 
> - A RAMFactor or similar will auto-increment its address register if you
> read its data register. In that case, it is probably innocuous, because
> the driver will set the address register before transferring data
> to/from it.
> 
> - Reading the input buffer register from a serial card will lose the
> received character.
> 

That was the case that came to mind, it clears the character available status.

> - Disk ][ controller motor control is activated by reading $C0n9.
> 
> > The best approach is to probably look for a ROM signature in the slot
> > first, and skip it unless its slot 3. I don't know of any other phantom
> > ROM except for the //e 80 column card that would be present in the same
> > slot as the Uthernet. Multi-IO perhaps?
> 
> The Apple IIgs, where some slots have built-in firmware mapped to $CnXX
> but don't use the $C0nX space for their I/O. For some of these, the I/O
> addresses are accessible from a card in the slot while the internal
> firmware is active. (I don't know if I still have enough reference
> material handy to confirm the details - I've thrown out most of my Apple
> II books and manuals due to water damage a few years ago.)

Right, probably like the mouse firmware on a //c or IIIgs.

> 
> > Other than that, if I poke something that doesn't work out, I try to
> > restore the value I found when I got there. I've had better success with
> > the Uthernet II than the Uthernet I (which I can find the first time, not
> > afterwards).
> 
> -- 
> David Empson
> dempson@actrix.gen.nz

Perhaps looking for a ROM *boot* signature would be better? There could be phantom disk slots though. Does the 3.5 drive firmware do that for slot 5? Ugh.

Dave...

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Re: Uthernet II manual updated, probe algorithm corrected D Finnigan <dog_cow@macgui.com> - 2016-01-08 17:49 +0000
  Re: Uthernet II manual updated, probe algorithm corrected David Schmenk <dschmenk@gmail.com> - 2016-01-08 22:38 -0800
    Re: Uthernet II manual updated, probe algorithm corrected D Finnigan <dog_cow@macgui.com> - 2016-01-09 21:33 +0000
      Re: Uthernet II manual updated, probe algorithm corrected David Schmenk <dschmenk@gmail.com> - 2016-01-09 14:24 -0800
        Re: Uthernet II manual updated, probe algorithm corrected dempson@actrix.gen.nz (David Empson) - 2016-01-10 15:07 +1300
          Re: Uthernet II manual updated, probe algorithm corrected David Schmenk <dschmenk@gmail.com> - 2016-01-10 07:56 -0800
            Re: Uthernet II manual updated, probe algorithm corrected dempson@actrix.gen.nz (David Empson) - 2016-01-11 10:11 +1300
              Re: Uthernet II manual updated, probe algorithm corrected David Schmenk <dschmenk@gmail.com> - 2016-01-11 08:59 -0800

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