atmega644v ATMEL Corporation, atmega644v Datasheet - Page 5

• Manufacturer Part Number: atmega644v
• Description: Atmega644 8-bit Avr Microcontroller With 64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

2.2.4
2.2.5
2.2.6
2.2.7
2.2.8
2.2.9
2593MS–AVR–08/07
Port B (PB7:PB0)
Port C (PC7:PC0)
Port D (PD7:PD0)
RESET
XTAL1
XTAL2
and source capability. As inputs, Port A pins that are externally pulled low will source current if
the pull-up resistors are activated. The Port A pins are tri-stated when a reset condition becomes
active, even if the clock is not running.
Port A also serves the functions of various special features of the ATmega644 as listed on
73.
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 ATmega644 as listed on
75.
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
ATmega644 as listed on
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 ATmega644 as listed on
80.
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
Characteristics” on page
Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
Output from the inverting Oscillator amplifier.
page
320. Shorter pulses are not guaranteed to generate a reset.
78.
ATmega644
”System and Reset
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