[En-Nut-Discussion] Ethernut 2.0 Alpha Schematic

[Austin Schutz]

On Tue, Oct 22, 2002 at 10:09:08PM +0200, Jarek Stojanowski wrote:
> 
> > Comments are most welcome.
> >
> > Harald
> 
> Hi Harald,
> 
> I've been thinking about something very simple. I want to leave lower space
> for cont memory and a15 for mem /CS, and use something like 3to8 decoder
> with a15 as 'oe' for upper memory space. I need 3 cs lines in upper mem
> range: 1 for asix and 2 for uart and I plan to add compactflash for
> monitoring app so it's leave some free lines for future use. Both asix and
> uart are 3V so if I use HC series chips 3V powered it should work.
> 
> Regards, Jarek
> 

	Ok, so here's one more idea:

	1. Leave 0x0000 - 0x7fff for controller
	2. Make 0x8000 - 0xbfff for decoded devices using 3to8 or 4to16
decoder
	3. Make 0xc000 - 0xffff for bank switched memory (~ 16k blocks)

	Another ugly schematic submitted. :-)

	This time by writing to any of 0x8000-0x83ff you would switch the
16k banks, and any other memory mapped devices would connect off the
multiplexor. You could attach one or more ethernet devices, plus any other
devices. 4to16 might be more than you want - it will segment the
0x8000-0xbfff in 1k blocks. Maybe 3to8 would be better?
	Are 16k memory banks large enough? I would tend to think they are.
	Also the schematic uses an inverting output decoder. Maybe it
would be simpler to use non-inverting.

	Austin

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