attiny24v ATMEL Corporation, attiny24v Datasheet - Page 55

• Manufacturer Part Number: attiny24v
• Description: 8-bit Avr Microcontroller With 2/4/8k Bytes Insystem Programmable Flash
• Manufacturer: ATMEL Corporation

10.1
10.1.1
8006H–AVR–10/09
Ports as General Digital I/O
Configuring the Pin
The ports are bi-directional I/O ports with optional internal pull-ups.
tional description of one I/O-port pin, here generically called Pxn.
Figure 10-2. General Digital I/O
Note:
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
Description” on page
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.
If PORTxn is written logic one when the pin is configured as an input pin, the pull-up resistor is
activated. To switch the pull-up resistor off, PORTxn has to be written logic zero or the pin has to
be configured as an output pin. The port pins are tri-stated when reset condition becomes active,
even if no clocks are running.
If PORTxn is written logic one when the pin is configured as an output pin, the port pin is driven
high (one). If PORTxn is written logic zero when the pin is configured as an output pin, the port
pin is driven low (zero).
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clk
Pxn
SLEEP, and PUD are common to all ports.
67, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits
PUD:
SLEEP:
clk
I/O
:
PULLUP DISABLE
SLEEP CONTROL
I/O CLOCK
(1)
SLEEP
SYNCHRONIZER
D
L
Q
Q
D
PINxn
Q
Q
RESET
RESET
PORTxn
WDx:
RDx:
WRx:
RRx:
RPx:
WPx:
Q
Q
Q
Q
DDxn
CLR
CLR
D
D
RRx
WRITE DDRx
READ DDRx
WRITE PORTx
READ PORTx REGISTER
READ PORTx PIN
WRITE PINx REGISTER
PUD
WDx
RDx
RPx
clk
ATtiny24/44/84
1
0
I/O
WRx
Figure 10-2
WPx
shows a func-
“Register
I/O
,
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