Damjan,

If you are building a data logger then the DRAM is a store that you might not mind a little bit-banging to use. This would save you a lot of hardware.

Are you familiar with DRAM? If you bit-bang you interface you can use two 8 bit ports and and your RAS,CAS, WR, strobes. No mux required.

Your refresh could be reading the 1st 256 bytes of memory when triggered by a timer (either burst or one each timeout) or in your idle loop.

You might want to check out:

http://www.semiconductors.philips.com/acrobat/8...t/8098.pdf

for some ideas.

regards,
p