ATmega16 datasheet(55/357 Pages) ATMEL

55 / 357 page

2466S–AVR–05/09

ATmega16(L)

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.

Alternate Port

Functions

Most port pins have alternate functions in addition to being General Digital I/Os. Figure 26

shows how the port pin control signals from the simplified Figure 23 can be overridden by alter-

nate 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.

Figure 26. Alternate Port Functions

(1)

Note:

1. WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clkI/O, SLEEP,

and PUD are common to all ports. All other signals are unique for each pin.

clk

RPx

RRx

WPx

RDx

WDx

PUD

SYNCHRONIZER

WDx:

WRITE DDRx

WPx:

WRITE PORTx

RRx:

READ PORTx REGISTER

RPx:

READ PORTx PIN

PUD:

PULLUP DISABLE

clk

I/O:

I/O CLOCK

RDx:

READ DDRx

SET

CLR

DIxn

AIOxn

DIEOExn

PVOVxn

PVOExn

DDOVxn

DDOExn

PUOExn

PUOVxn

PUOExn:

Pxn PULL-UP OVERRIDE ENABLE

PUOVxn:

Pxn PULL-UP OVERRIDE VALUE

DDOExn:

Pxn DATA DIRECTION OVERRIDE ENABLE

DDOVxn:

Pxn DATA DIRECTION OVERRIDE VALUE

PVOExn:

Pxn PORT VALUE OVERRIDE ENABLE

PVOVxn:

Pxn PORT VALUE OVERRIDE VALUE

DIxn:

DIGITAL INPUT PIN n ON PORTx

AIOxn:

ANALOG INPUT/OUTPUT PIN n ON PORTx

RESET

CLR

PINxn

PORTxn

DDxn

DIEOVxn

SLEEP

DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE

DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE

SLEEP:

SLEEP CONTROL

Pxn

I/O

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