Rainbow Electronics ATmega1284P - Manual (Page 5)

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8059CS–AVR–07/09
ATmega1284P
2.2.4 Port B (PB7:PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port B output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port B pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port B also serves the functions of various special features of the ATmega1284P as listed on
page 81 .
2.2.5 Port C (PC7:PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port C output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port C pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port C also serves the functions of the JTAG interface, along with special features of the
ATmega1284P as listed on
page 84 .
2.2.6 Port D (PD7:PD0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port D output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port D pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port D also serves the functions of various special features of the ATmega1284P as listed on
page 87 .
2.2.7 RESET
Reset input. A low level on this pin for longer than the minimum pulse length will generate a
reset, even if the clock is not running. The minimum pulse length is given in
”System and Reset
Characteristics” on page 328 . Shorter pulses are not guaranteed to generate a reset.
2.2.8 XTAL1
Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
2.2.9 XTAL2
Output from the inverting Oscillator amplifier.
2.2.10 AVCC
AVCC is the supply voltage pin for Port F and the Analog-to-digital Converter. It should be exter-
nally connected to V
CC
, even if the ADC is not used. If the ADC is used, it should be connected
to V
CC
through a low-pass filter.
2.2.11 AREF
This is the analog reference pin for the Analog-to-digital Converter.