Alternate port functions, Data b u s – Rainbow Electronics ATmega3290P_V User Manual
Page 65
65
ATmega329/3210/649/6410
2552H–AVR–11/06
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
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
27 shows how the port pin control signals from the simplified Figure 24 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 27. Alternate Port Functions
(1)
Note:
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port.
clk
I/O
, SLEEP, and PUD are common to all ports. All other signals are unique for each
pin.
clk
RPx
RRx
WRx
RDx
WDx
PUD
SYNCHRONIZER
WDx:
WRITE DDRx
WRx:
WRITE PORTx
RRx:
READ PORTx REGISTER
RPx:
READ PORTx PIN
PUD:
PULLUP DISABLE
clk
I/O
:
I/O CLOCK
RDx:
READ DDRx
D
L
Q
Q
SET
CLR
0
1
0
1
0
1
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
RESET
Q
Q
D
CLR
Q
Q
D
CLR
Q
Q
D
CLR
PINxn
PORTxn
DDxn
D
ATA
B
U
S
0
1
DIEOVxn
SLEEP
DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
SLEEP:
SLEEP CONTROL
Pxn
I/O
0
1
PTOExn
WPx
PTOExn:
Pxn, PORT TOGGLE OVERRIDE ENABLE
WPx:
WRITE PINx