AT90USB646 datasheet(75/456 Pages) ATMEL

75 / 456 page

7593L–AVR–09/12

AT90USB64/128

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.

11.2.5

Digital input enable and sleep modes

As shown in Figure 11-2 on page 72, 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 76.

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.

11.2.6

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 described above, float-

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;

...

AT90USB646 Datasheet(PDF) 75 Page - ATMEL Corporation

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