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
pullup. In this case, the pullup will be disabled during reset. If low power consumption
during reset is important, it is recommended to use an external pullup or pulldown. Con-
necting 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.
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 overrid-
den 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 micro-
controller family.
Figure 26. Alternate Port Functions(1)
PUOExn
PUOVxn
1
PUD
0
DDOExn
DDOVxn
1
Q
D
0
DDxn
Q CLR
WDx
RDx
PVOExn
PVOVxn
RESET
1
0
Pxn
Q
D
PORTxn
Q CLR
DIEOExn
DIEOVxn
SLEEP
WPx
RRx
RESET
1
0
SYNCHRONIZER
RPx
SET
D
Q
D
L
Q
Q
PINxn
CLR Q
CLR
clk I/O
DIxn
AIOxn
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
PUD:
WDx:
RDx:
RRx:
WPx:
RPx:
PULLUP DISABLE
WRITE DDRx
READ DDRx
READ PORTx REGISTER
WRITE PORTx
READ PORTx PIN
DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
clkI/O
DIxn:
AIOxn:
:
I/O CLOCK
DIGITAL INPUT PIN n ON PORTx
ANALOG INPUT/OUTPUT PIN n ON PORTx
SLEEP:
SLEEP CONTROL
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.
54
ATmega32(L)
2503J–AVR–10/06
ATMEL [ ATMEL ]
