Datasheet

41
ATtiny4/5/9/10 [DATASHEET]
8127F–AVR–02/2013
10.2 Ports as General Digital I/O
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 10-2 shows a functional description of
one I/O-port pin, here generically called Pxn.
Figure 10-2. General Digital I/O
(1)
Note: 1. WEx, WRx, WPx, WDx, REx, RRx, RPx, and RDx are common to all pins within the same port. clk
I/O
, and SLEEP
are common to all ports.
10.2.1 Configuring the Pin
Each port pin consists of four register bits: DDxn, PORTxn, PUExn, and PINxn. As shown in “Register Description”
on page 50, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits at the PORTx I/O address, the
PUExn bits at the PUEx 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
WEx
SYNCHRONIZER
WDx: WRITE DDRx
WRx: WRITE PORTx
RRx: READ PORTx REGISTER
RPx: READ PORTx PIN
clk
I/O
: I/O CLOCK
RDx: READ DDRx
WEx: WRITE PUEx
REx: READ PUEx
D
L
Q
Q
REx
RESET
RESET
Q
QD
Q
QD
CLR
PORTxn
Q
QD
CLR
DDxn
PINxn
DATA BUS
SLEEP
SLEEP: SLEEP CONTROL
Pxn
I/O
WPx
RESET
Q
QD
CLR
PUExn
0
1
WRx
WPx: WRITE PINx REGISTER