Digital input enable and sleep modes, Digital input, Atmega128(l) – Rainbow Electronics ATmega128L User Manual
Page 65
65
ATmega128(L)
2467B–09/01
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 29, 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
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
...
; 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
in
r16,PINB
...
C Code Example
unsigned char i;
...
/* 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;
...