50
8126F–AVR–05/12
ATtiny13A
Note that enabling the alternate function of some of the port pins does not affect the use of the
other pins in the port as general digital I/O.
10.2
Ports as General Digital I/O
The ports are bi-directional I/O ports with optional internal pull-ups.
shows a functional description of one I/O-port pin, here generically called Pxn.
Figure 10-2.
General Digital I/O
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.
10.2.1
Configuring the Pin
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits
at the PORTx I/O address, and the PINxn bits at the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written logic one,
Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input
pin.
clk
RPx
RRx
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
RESET
RESET
Q
Q
D
Q
Q
D
CLR
PORTxn
Q
Q
D
CLR
DDxn
PINxn
D
ATA
B
U
S
SLEEP
SLEEP:
SLEEP CONTROL
Pxn
I/O
WPx
0
1
WRx
WPx:
WRITE PINx REGISTER