AVR-Chat

I don't think you'll be happy with trying the make that interface work at
full speed( 96kHz ). At the 32 bits you mentioned ( I assume you're looking
at 16 bit frames for each channel... ) you are looking at a transfer rate of
~3.1Mbps, running at 20MHz every ~50th instruction would have to save data
to memory, possible but not wonderful.  If you can figure out how to use the
hardware for some things you might be in better shape also.

Basically can you run a spectrum analyzer real time on an AVR... with that
data source I doubt it, but you certainly have time to store it to memory.
All things considered though I think I'd look at either reducing the data
rate, the AD1871 supports 48kHz also, or going to a more powerful chip.  If
the data rate is a requirement and you aren't in a hurry you might want to
wait for the new 32 bit AVR, having perused the architecture document a
couple times it looks to be an excellent chip for this type of thing.  If,
indeed time is a factor also you might want to consider the Atmel SAM series
ARM chips.  I can't say that I know much about compiler availability ( I'm
waiting for the AVR32 ) but the hardware USART would be up to the job, and
the ability to handle larger chunks of data would make things much easier...
not the mention a 50MHz clock vs. 20MHz for the AVR.

Martin Jay McKee