attiny13-20ss ATMEL Corporation, attiny13-20ss Datasheet - Page 47

• Manufacturer Part Number: attiny13-20ss
• Description: 8-bit Microcontroller With 1k Bytes In-system Programmable Flash - Atmel Corporation
• Manufacturer: ATMEL Corporation

Digital Input Enable and Sleep
Modes
2535G–AVR–01/07
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 5 as input with a pull-up assigned to port pin 4. The result-
ing 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:
As shown in Figure 21, 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
SLEEP is overridden for port pins enabled as external interrupt pins. If the external inter-
rupt 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 48.
If a logic high level (“one”) is present on an asynchronous external interrupt pin config-
ured 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
Assembly Code Example
C Code Example
unsigned char i;
...
; Define pull-ups and set outputs high
; Define directions for port pins
ldi
ldi
out
out
; Insert nop for synchronization
nop
; Read port pins
in
...
...
/* Define pull-ups and set outputs high */
/* Define directions for port pins */
PORTB = (1<<PB4)|(1<<PB1)|(1<<PB0);
DDRB = (1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0);
/* Insert nop for synchronization*/
__no_operation();
/* Read port pins */
i = PINB;
...
1. For the assembly program, two temporary registers are used to minimize the time
CC
from pull-ups are set on pins 0, 1 and 4, until the direction bits are correctly set, defin-
ing bit 2 and 3 as low and redefining bits 0 and 1 as strong high drivers.
/2.
r16,(1<<PB4)|(1<<PB1)|(1<<PB0)
r17,(1<<DDB3)|(1<<DDB2)|(1<<DDB1)|(1<<DDB0)
PORTB,r16
DDRB,r17
r16,PINB
(1)
47