ATMEGA128-8AI ATMEL Corporation, ATMEGA128-8AI Datasheet - Page 6

• Manufacturer Part Number: ATMEGA128-8AI
• Description: 8-bit Microcontroller with 128K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Port D (PD7..PD0)
Port E (PE7..PE0)
Port F (PF7..PF0)
Port G (PG4..PG0)
RESET
XTAL1
6
ATmega128(L)
Port C also serves the functions of special features of the ATmega128 as listed on page
72 . In ATmega103 compatibility mode, Port C is output only, and the port C pins are not
tri-stated when a reset condition becomes active.
Port D is an 8-bit bidirectional 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 ATmega128 as listed
on page 73 .
Port E is an 8-bit bidirectional I/O port with internal pull-up resistors (selected for each
bit). The Port E output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port E pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port E pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port E also serves the functions of various special features of the ATmega128 as listed
on page 76 .
Port F serves as the analog inputs to the A/D Converter.
Port F also serves as an 8-bit bi-directional I/O port, if the A/D Converter is not used.
Port pins can provide internal pull-up resistors (selected for each bit). The Port F output
buffers have symmetrical drive characteristics with both high sink and source capability.
As inputs, Port F pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port F pins are tri-stated when a reset condition becomes
active, even if the clock is not running. If the JTAG interface is enabled, the pull-up resis-
tors on pins PF7(TDI), PF5(TMS) and PF4(TCK) will be activated even if a reset occurs.
Port F also serves the functions of the JTAG interface.
In ATmega103 compatibility mode, Port F is an input Port only.
Port G is a 5-bit bidirectional I/O port with internal pull-up resistors (selected for each
bit). The Port G output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port G pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port G pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port G also serves the functions of various special features.
The port G pins are tri-stated when a reset condition becomes active, even if the clock is
not running.
In ATmega103 compatibility mode, these pins only serves as strobes signals to the
external memory as well as input to the 32 kHz oscillator, and the pins are initialized to
PG0 = 1, PG1 = 1, and PG2 = 0 asynchronously when a reset condition becomes active,
even if the clock is not running. PG3 and PG4 are oscillator pins.
Reset input. A low level on this pin for longer than the minimum pulse length will gener-
ate a reset, even if the clock is not running. The minimum pulse length is given in Table
19 on page 46 . Shorter pulses are not guaranteed to generate a reset.
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
2467AS–08/01