Rainbow-electronics ATmega8HVD Manuel d'utilisateur télécharger pdf (Page 66)

8052B–AVR–09/08

ATmega4HVD/8HVD

14.2.6 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 V

or GND is not recommended, since this may cause excessive cur-

rents if the pin is accidentally configured as an output.

14.3 Alternate Port Functions

Many low voltage port pins have alternate functions in addition to being general digital I/Os.

Figure 14-5 on page 67 shows how the port pin control signals from the simplified Figure 14-2

on page 62 can be overridden by alternate functions. The overriding signals may not be pres-

ent in all port pins, but the figure serves as a generic description applicable to all port pins in

the AVR microcontroller family.

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Rainbow-electronics ATmega8HVD Manuel d'utilisateur Page 66