ATmega128 datasheet(6/386 Pages) ATMEL

6 / 386 page

2467S–AVR–07/09

ATmega128

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 special features of the ATmega128 as listed on page 77. In

ATmega103 compatibility mode, Port C is output only, and the port C pins are not tri-stated

when a reset condition becomes active.

Note:

The ATmega128 is by default shipped in ATmega103 compatibility mode. Thus, if the parts are not

programmed before they are put on the PCB, PORTC will be output during first power up, and until

the ATmega103 compatibility mode is disabled.

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 ATmega128 as listed on page

78.

Port E (PE7..PE0)

Port E is an 8-bit bi-directional 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

81.

Port F (PF7..PF0)

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 sym-

metrical 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 resistors on pins PF7(TDI), PF5(TMS), and PF4(TCK) will

be activated even if a Reset occurs.

The TDO pin is tri-stated unless TAP states that shift out data are entered.

Port F also serves the functions of the JTAG interface.

In ATmega103 compatibility mode, Port F is an input Port only.

Port G (PG4..PG0)

Port G is a 5-bit bi-directional 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.

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