Datasheet

60
7701F–AVR–10/12
Atmel ATtiny24/44/84 [Preliminary]
The following code example shows how to set port A pins 0 and 1 high, 2 and 3 low, and
define the port pins from 4 to 5 as input with a pull-up assigned to port pin 4. The resulting pin
values are read back again, but as previously discussed, a nop instruction is included to be
able to read back the value recently assigned to some of the pins.
Note: 1. For the assembly program, two temporary registers are used to minimize the time from
pull-ups are set on pins 0, 1 and 4, until the direction bits are correctly set, defining bit 2 and
3 as low and redefining bits 0 and 1 as strong high drivers.
12.2.5 Digital Input Enable and Sleep Modes
As shown in Figure 12-2 on page 57, the digital input signal can be clamped to ground at the
input of the schmitt-trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep
Controller in Power-down mode, Power-save mode, and Standby mode to avoid high power
consumption if some input signals are left floating, or have an analog signal level close to
V
CC
/2.
SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt
request is not enabled, SLEEP is active also for these pins. SLEEP is also overridden by vari-
ous other alternate functions as described in “Alternate Port Functions” on page 61.
Assembly Code Example
(1)
...
; Define pull-ups and set outputs high
; Define directions for port pins
ldi r16,(1<<PA4)|(1<<PA1)|(1<<PA0)
ldi r17,(1<<DDA3)|(1<<DDA2)|(1<<DDA1)|(1<<DDA0)
out PORTA,r16
out DDRA,r17
; Insert nop for synchronization
nop
; Read port pins
in r16,PINA
...
C Code Example
unsigned char i;
...
/* Define pull-ups and set outputs high */
/* Define directions for port pins */
PORTA = (1<<PA4)|(1<<PA1)|(1<<PA0);
DDRA = (1<<DDA3)|(1<<DDA2)|(1<<DDA1)|(1<<DDA0);
/* Insert nop for synchronization*/
_NOP();
/* Read port pins */
i = PINA;
...