ATmega64A datasheet(72/392 Pages) ATMEL

72 / 392 page

8160C–AVR–07/09

ATmega64A

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.

13.2.3

Digital Input Enable and Sleep Modes

As shown in Figure 13-2, 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, Standby mode, and Extended 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 73.

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

“Interrupt on Any Logic Change on Pin” while the External Interrupt is not enabled, the corre-

sponding External Interrupt Flag will be set when resuming from the above mentioned sleep

modes, as the clamping in these sleep modes 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*/

_NOP();

/* Read port pins */

i = PINB;

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