ATmega328P datasheet(71/345 Pages) ATMEL

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7810A–AVR–11/09

ATmega328P [Preliminary]

13.2.6

Unconnected Pins

If some pins are unused, it is recommended to ensure that these pins have a defined level. Even

though most of the digital inputs are disabled in the deep sleep modes as described above, float-

ing inputs should be avoided to reduce current consumption in all other modes where the digital

inputs are enabled (Reset, Active mode and Idle mode).

The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up.

In this case, the pull-up will be disabled during reset. If low power consumption during reset is

important, it is recommended to use an external pull-up or pull-down. Connecting unused pins

directly to V

CC or GND is not recommended, since this may cause excessive currents if the pin is

accidentally configured as an output.

13.3

Alternate Port Functions

Most port pins have alternate functions in addition to being general digital I/Os. Figure 13-5

shows how the port pin control signals from the simplified Figure 13-2 on page 67 can be over-

ridden by alternate functions. The overriding signals may not be present in all port pins, but the

figure serves as a generic description applicable to all port pins in the AVR microcontroller

family.

ATmega328P 데이터시트(PDF) 71 Page - ATMEL Corporation