I have an Arduino ADK board. I'm trying to use a built-in variable to monitor the digital input pins. For example, on my Arduino UNO
PORTD maps to Arduino digital pins 0 to 7
PIND - The Port D Input Pins Register - read only
With the UNO I can use the PIND variable successfully to monitor activity on the pins 0-7. However, this is not working with the ADK board. Although the "PIND" variable is defined I don't know what it maps to and I cannot find the info. For the UNO, there is this web page:http://www.arduino.cc/en/Reference/PortManipulation
However, the page doesn't include the ADK's ATmega2560. How can I find the correct variable to use (if there even is one)?