ATTINY261_09 Datasheet, PDF (60/227 Pages) ATMEL Corporation – 8-bit Microcontroller with 2/4/8K Bytes In-System Programmable Flash

12.2.6
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.
12.3
Alternate Port Functions
Most port pins have alternate functions in addition to being general digital I/Os. Figure 12-5
shows how the port pin control signals from the simplified Figure 12-2 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.
60 ATtiny261/ATtiny461/ATtiny861
7753C–AVR–07/09