ATtiny43U datasheet(66/182 Pages) ATMEL

66 / 182 page

8048B–AVR–03/09

ATtiny43U

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.

11.2.5

Digital Input Enable and Sleep Modes

As shown in Figure 11-2 on page 63, 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 various

other alternate functions as described in “Alternate Port Functions” on page 67.

If a logic high level (“one”) is present on an asynchronous external interrupt pin configured as

“Interrupt on Rising Edge, Falling Edge, or Any Logic Change on Pin” while the external interrupt

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

r16,PINA

...

C Code Example

unsigned char

...

/* 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;

...

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