Rainbow Electronics ATmega8HVD - Manual (Page 65)

65
8052B–AVR–09/08
ATmega4HVD/8HVD
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.
14.2.5 Digital Input Enable and Sleep Modes
As shown in Figure 14-2 on page 62 , 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-save 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 vari-
ous other alternate functions as described in
”Alternate Port Functions” on page 66 .
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 inter-
rupt 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<
ldi r17,(1<
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<
DDRB = (1<
/* Insert nop for synchronization*/
_NOP();
/* Read port pins */
i = PINB;
...