Rainbow-electronics ATmega8515L Uživatelský manuál stáhnout pdf (Strana 60)

ATmega8515(L)

2512A–AVR–04/02

The following codeexample shows how to set port Bpins 0and 1 high, 2and3low, and

define the port pinsfrom 4 to 7 as input withpull-ups assigned to port pins6and7.The

resulting pin values are readback again,but aspreviously discussed, a

nop

instruction

is included to beabletoreadback thevalue recently assigned to some of the pins.

Note: 1. For theassembly program, twotemporary registers areused to minimizethetime

from pull-ups are set on pins 0, 1,6,and7,until the direction bits are correctly set,

defining bit 2 and3aslow andredefining bits 0and 1asstrong highdrivers.

Digital Input Enable and Sleep

Modes

AsshowninFigure29, the digital input signalcan be clamped to ground at theinput of

the schmitt-trigger.The signaldenotedSLEEPinthe figure, isset by the MCU Sleep

Controller in Power-downmodeandStandby modetoavoidhighpowerconsumption if

some input signals are left floating, orhave an analog signallevelclosetoV

/2.

SLEEPis overridden forport pins enabled asExternalInterrupt pins. If the External

InterruptRequestis not enabled, SLEEPis active also for these pins. SLEEPis also

overridden by various other alternate functions asdescribed in “Alternate Port Func-

tions”onpage 61.

If a logichighlevel(“one”) ispresent on an AsynchronousExternalInterrupt pin config-

ured as “InterruptonAnyLogicChange on Pin” whiletheexternal interruptis

not

enabled, the corresponding ExternalInterrupt Flag will be set when resuming from the

above mentionedsleep modes, as the clamping in these sleep modesproduces the

requestedlogicchange.

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

in r16,PINB

...

CCode 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;

...

1 2 ... 55 56 57 58 59 60 61 62 63 64 65 ... 222 223

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