Atmel provides an Application Note on this exact topic titled "Iterfacing
the 3-volt DataFlash with a 5-volt System." The bottom line is that the
DataFlash's inputs are 5-volt tolerant, so you have no problems connecting
SCK, CS', RESET', WP' and SI directly. The only line that you have to
concern yourself with is SO, which has to provide a 5-Volt compatible signal
for the 18F452. The Application Note recommends the MAX3370 level shifter
for the task, and I've used this part with success. One problem for small
production though, I had to order them directly from Maxim, which wasn't a
problem for me as I ordered 1000's.

On a separate note, during prototyping I configured several buffers(level
shifters) using FETs and analog switches, with success. In fact, when one
buffer burned out, I connected the DataFlash directly to the PIC and the SO
signals were sufficient for reliable communications, even though a look at
the PIC's datasheet would suggest that this is not a great idea.

Good luck, Shawn.

Bob Japundza wrote:
I was wondering how you would connect an Atmel AT45DBxxxx dataflash chip to
a pic.  Being the pic I'm using (18F452) is 5v, and the AT45 is 2.7, how
does one connect one of these via SPI?  I was thinking about doing this with
some opamps but am not sure yet how I would go about doing it.  I would like
to have other devices on my SPI bus so I don't want to do anything that may
screw things up.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads