IIM7010A 3.3v connected directly to 5V AVR?

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I'd like to connect a Wiznet IIM7010A ethernet module
(W3100A chip) to a 5V ATmega128 microcontroller's parallel bus.

The IIM7010A operates at 3.3v bus has 5V tolerant I/Os.
I've seen some mention of connecting it directly to a 5V
microcontroller's memory bus, and it seems that there would
be no problem for the uC's 5V outputs connected to the IIM7010A.

But the minimum high level for the IIM7010A is listed as
2.4V - whereas the ATmega128 wants 0.6 * VCC - which would
mean it needs 3.0v @ 5V for a valid high.

Does this mean that I would need to use some sort of level
shifter for the output pins of the IIM7010A to make sure
they are always above 3.0v when high?  Or can it work
reliably using the internal pullups of the ATmega128's
memory bus?

Are there any things to watch out for when connecting these?

Does anyone have a sample schematic for a similar setup with
the IIM7010A at 3.3V and a microcontroller at 5V?


Thanks.




Re: IIM7010A 3.3v connected directly to 5V AVR?
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This will work. The minimum level for a '1' at 2.4V is under maximum load
conditions and with just one micro on the bus it will be almost 3.3V.

I am doing a similar thing with a Bluetooth module at 3.3V. The signals from
the micro are lowered with a simple 2-resistor divider while the signals
from the BT module (at 3.3V) run directly to the micro at 5V.

Meindert



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