ATMEGA640 datasheet(72/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

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, floating 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 VCC 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 on page 73 shows how

the port pin control signals from the simplified Figure 13-2 on page 68 can be overridden 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.

ATMEGA640 Datasheet(PDF) 72 Page - Microchip Technology