ATMEGA649 datasheet(64/375 Pages) ATMEL

64 / 375 page

ATmega329/3210/649/6410

2552H–AVR–11/06

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 24, 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 65.

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.

Unconnected Pins

If some pins are unused, it is recommended to ensure that these pins have a defined

level. Even though most of the digital inputs are disabled in the deep sleep modes as

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;

...

ATMEGA649 Datasheet(PDF) 64 Page - ATMEL Corporation

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