ATmega16 datasheet(51/315 Pages) ATMEL

51 / 315 page

ATmega16(L)

2466E–AVR–10/02

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, 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 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 Func-

tions” on page 52.

If a logic high level (“one”) is present on an Asynchronous External Interrupt pin config-

ured as “Interrupt on 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 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(1)

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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