ATmega640/1280/1281/2560/2561
above mentioned Sleep mode, as the clamping in these sleep mode produces the requested
logic change.
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 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
shows how the port pin control signals from the simplified Figure 13-2 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.
75
2549L–AVR–08/07
ATMEL [ ATMEL ]
