ATMEGA640 datasheet(71/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

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.

13.2.5

Digital Input Enable and Sleep Modes

As shown in Figure 13-2 on page 68, 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 VCC/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 72.

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 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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