Re: A85: Memory Mapped Devices


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Re: A85: Memory Mapped Devices



As you guessed, the "chips" are just 74-series logic glue. Technically
they don't *have* to be 74-series, but that's what would most likely be
used in prototype projects. I'll scan a drawing from a book I've got (it
just happens to be about 68k processos) and post it on my web page.

-- 
Greg Hill
greg-hill@bigfoot.com
www.comports.com/link



On Wed, 29 Oct 1997, Keith Burzinski wrote:

> A.K.A. TheWiz wrote:
> > 
> > > Does anyone know how Memory Mapping is done?  Like, for example, the
> > > screen on the TI-85 or 92?  I'm not looking for anything real
> > > specific,
> > > just a somewhat general explination as to how it is done/how it
> > > works.
> > > And actually, something more from a hardware standpoint.  ;)
> > 
> >   Various chips are used to determine the address being read/written,
> > and if
> > it's in a certain range (usually having high bits set down to a
> > certain one,
> > which is why VRAM on the calculator is at the end), it's sent to the
> > mapped-in device.
> Where can I get these "chips"?  ;)  Or is it just logic?  If it's logic,
> anyone got any schematics I might look at?  ;)
> 
> 
> >   HTH.
> ISD.
> 
> Cheers,
> --
> ~Keith
> TSK3000@Prodigy.Net
> 


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