Power Pins; Memory; Input And Output - Arduino Mega ADK User Manual

The power pins are as follows:
VIN. The input voltage to the Arduino board when it's using an external power source (as
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opposed to 5 volts from the USB connection or other regulated power source). You can
supply voltage through this pin, or, if supplying voltage via the power jack, access it through
this pin.
5V. This pin outputs a regulated 5V from the regulator on the board. The board can be
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supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the
VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the
regulator, and can damage your board. We don't advise it.
3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.
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GND. Ground pins.
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IOREF. This pin on the Arduino board provides the voltage reference with which the
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microcontroller operates. A properly configured shield can read the IOREF pin voltage and
select the appropriate power source or enable voltage translators on the outputs for working
with the 5V or 3.3V.

Memory

The MEGA ADK has 256 KB of flash memory for storing code (of which 8 KB is used for the
bootloader), 8 KB of SRAM and 4 KB of EEPROM (which can be read and written with
the EEPROM library).

Input and Output

Each of the 50 digital pins on the MEGA ADK can be used as an input or output, using pin
Mode (),digitalWrite(), and digital Read() functions. They operate at 5 volts. Each pin can
provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by
default) of 20-50 kOhms. In addition, some pins have specialized functions:
Serial: 0 (RX) and 1 (TX); Serial 1: 19 (RX) and 18 (TX); Serial 2: 17 (RX) and 16 (TX); Serial
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3: 15 (RX) and 14 (TX). Used to receive (RX) and transmit (TX) TTL serial data. Pins 0 and 1
are also connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip.
External Interrupts: 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20
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(interrupt 3), and 21 (interrupt 2). These pins can be configured to trigger an interrupt on a
low value, a rising or falling edge, or a change in value. See the attach Interrupt () function
for details.
PWM: 2 to 13 and 44 to 46. Provide 8-bit PWM output with the analog Write () function.
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SPI: 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS). These pins support SPI communication using
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the SPI library. The SPI pins are also broken out on the ICSP header, which is physically
compatible with the Uno, Duemilanove and Diecimila.
USB Host: MAX3421E.
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