ATmega165 datasheet(59/336 Pages) ATMEL

59 / 336 page

ATmega165/V

2573G–AVR–07/09

The following code example shows how to set port B pins 0 and 1 high, 2 and 3 low, and

define the port pins from 4 to 7 as input with pull-ups assigned to port pins 6 and 7. 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, 6, and 7, until the direction bits are correctly set,

defining bit 2 and 3 as low and redefining bits 0 and 1 as strong high drivers.

Digital Input Enable and Sleep

Modes

As shown in Figure 23, 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 inter-

rupt 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 Func-

tions” on page 60.

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

ured as “Interrupt on Rising Edge, Falling Edge, or Any Logic Change on Pin” while the

external interrupt is not enabled, the corresponding External Interrupt Flag will be set

when resuming from the above mentioned Sleep mode, as the clamping in these sleep

mode produces the requested logic change.

Assembly Code Example(1)

...

; Define pull-ups and set outputs high

; Define directions for port pins

ldi

r16,(1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0)

ldi

r17,(1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0)

out

PORTB,r16

out

DDRB,r17

; Insert nop for synchronization

nop

; Read port pins

r16,PINB

...

C Code Example

unsigned char

...

/* Define pull-ups and set outputs high */

/* Define directions for port pins */

PORTB = (1<<PB7)|(1<<PB6)|(1<<PB1)|(1<<PB0);

DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);

/* Insert nop for synchronization*/

__no_operation();

/* Read port pins */

i = PINB;

...

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