AVR inputs = high impedance, yes?

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I can't believe I've never come into this situation before - but well - everything I do with AVRs tends to be with peripherals and/or outputs - I never directly use the inputs. With that said - I need to connect 10 input pins on an ATMEGA88 to an FPGA. When DDRxx = 0 that pin is configured as a high impedance input, right?

I feel dumb.

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Look at this:

DDR PORT | Result
---------+-------
 0    0  | Input hi-impedance.  PIN = input voltage
 0    1  | Input with internal pull-up resistor to VCC.  PIN = input voltage
 1    0  | Output LOW.  PIN = LOW after couple of clocks.
 1    1  | Output HIGH.  PIN = HIGH after couple of clocks.
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You can also have inputs with internal pullup "resistor".

Jim

 

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The pullup resistor is nice because it helps eliminate noise from nearby lines.

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