Re: A85: Memory Mapped Devices
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Re: A85: Memory Mapped Devices
> > 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? ;)
It's logic. Via chips (usually). What you want is a circuit that takes a
binary number, about 2-3 bits long, and outputs a single signal on one of
several (4, 8, ...) lines to tell the device it's selected. Called a decoder,
logically enough.
If you're familiar with electronics, you could perhaps come up with a
circuit, but it would probably be easier and cheaper to order a chip from an
electronics supplier. Ask for catalogs from www.mouser.com and
www.digikey.com, and you might have a use for the chip index at
http://www.hitex.com/chipdir/.
> > HTH.
> ISD.
What do you know, I've never heard that one. What is it?
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