[En-Nut-Discussion] Ethernut 2.0 Alpha Schematic

[Austin Schutz]

On Tue, Oct 22, 2002 at 04:51:45PM +0200, Harald Kipp wrote:
> Regarding your bank switching schematics:
> 
> Should work upto a certain point. The problem is,
> that it leaves no room for the Ethernet Controller.
> Using one of the bank switching register outputs
> would be no good idea. Transfering data to a memory
> bank would be too time consuming.
> 
> The 91C111 provides an output, which is set when
> the address bus matches the internal address decoder.
> This would simplify things a lot, but the Asix
> Controller doesn't provide such an output.
> 

	That would help, certainly.  You could tie the output to CS/ on the
sram. You might have timing issues, depending on how fast it sets the output.

	Another alternative would be to add a 4 to 16 decoder, and connect the
output line for the ethernet to CS/ on the sram. The disadvantages would be
taking up more space on the board and losing 1k of low ram space, though it
would make it much easier to add additional memory mapped devices to the bus
in the future.
	Btw, I get 1k from looking at the 74xx154, which has 2 extra inputs
for not decoding at all, which could be tied to A14/A15:
  http://www.ee.washington.edu/stores/DataSheets/74ls/74ls154.pdf

	Austin