ATMEGA169 ATMEL [ATMEL Corporation], ATMEGA169 Datasheet - Page 60

• Manufacturer Part Number: ATMEGA169
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Unconnected Pins
Alternate Port Functions
60
ATmega169/V
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
cause excessive currents if the pin is accidentally configured as an output.
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
Note:
PUOExn:
PUOVxn:
DDOExn:
DDOVxn:
PVOExn:
PVOVxn:
DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
SLEEP:
PTOExn:
Pxn
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port.
Pxn PULL-UP OVERRIDE ENABLE
Pxn PULL-UP OVERRIDE VALUE
Pxn DATA DIRECTION OVERRIDE ENABLE
Pxn DATA DIRECTION OVERRIDE VALUE
Pxn PORT VALUE OVERRIDE ENABLE
Pxn PORT VALUE OVERRIDE VALUE
SLEEP CONTROL
Pxn, PORT TOGGLE OVERRIDE ENABLE
clk
pin.
I/O
, SLEEP, and PUD are common to all ports. All other signals are unique for each
1
0
1
0
1
0
1
0
PUOExn
PUOVxn
PVOExn
PVOVxn
DIEOExn
DIEOVxn
SLEEP
DDOExn
DDOVxn
(1)
CC
or GND is not recommended, since this may
PUD:
WDx:
RDx:
RRx:
WRx:
RPx:
clk
DIxn:
AIOxn:
SYNCHRONIZER
WPx:
D
L
I/O
SET
CLR
:
Q
Q
PULLUP DISABLE
WRITE DDRx
READ DDRx
READ PORTx REGISTER
WRITE PORTx
READ PORTx PIN
WRITE PINx
I/O CLOCK
DIGITAL INPUT PIN n ON PORTx
ANALOG INPUT/OUTPUT PIN n ON PORTx
D
PINxn
CLR
Q
Q
RESET
RESET
PORTxn
Q
Q
Q
Q
DDxn
CLR
CLR
D
D
1
0
clk
PUD
WDx
RDx
RRx
DIxn
AIOxn
RPx
I/O
WRx
2514P–AVR–07/06
PTOExn
WPx