參數(shù)資料
型號: MC80C52XXX-16SHXXX:D
廠商: TEMIC SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CDIP40
文件頁數(shù): 126/141頁
文件大?。?/td> 7628K
55
2486AA–AVR–02/2013
ATmega8(L)
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 22 on page 52, 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 Control-
ler 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 vari-
ous other alternate functions as described in “Alternate Port Functions” on page 56.
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 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;
...
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