Rainbow-electronics ATmega8515L Manual do Utilizador descarregar pdf (Página 96)

ATmega8515(L)

2512A–AVR–04/02

also set the Compare Match Flag (OCF1A/B) which can beused to generate an output

compareinterrupt request.

The Input Capture Registercan capturetheTimer/Counter value at a given external

(edge triggered) event on either the Input CapturePin(ICP1) or on theAnalog Compar-

atorpins(See “Analog Comparator”onpage 160.) Theinput captureunitincludes a

digitalfiltering unit (Noise Canceler) forreducing the chanceofcapturing noise spikes.

TheTOPvalue, or maximum Timer/Counter value,can in some modes of operation be

definedbyeither the OCR1A Register, the ICR1 Register, orbya set offixed values.

When using OCR1A as TOPvalueinaPWM mode, the OCR1A Registercan not be

usedfor generating a PWM output. However, theTOPvalue will in thiscase be double

buffered allowing theTOPvalue to be changed in run time. If a fixed TOPvalue is

required, the ICR1 registercan beused as an alternative,freeing the OCR1A to beused

as PWM output.

Definitions The following definitions areused extensively throughout the document:

Compatibility The16-bit Timer/Counterhasbeen updated and improvedfrom previous versions of the

16-bit AVR Timer/Counter.This 16-bit Timer/Counter isfully compatible with theearlier

version regarding:

•All 16-bit Timer/CounterrelatedI/O Register address locations, including timer

interrupt registers.

• Bit locations insideall 16-bit Timer/Counter Registers, including timer interrupt

registers.

• InterruptVectors.

The following controlbitshave changed name,but have same functionality andregister

location:

•PWM10 ischanged to WGM10.

•PWM11 ischanged to WGM11.

• CTC1ischanged to WGM12.

The following bits areadded to the16-bit Timer/CounterControl Registers:

• FOC1A andFOC1B areadded to TCCR1A.

• WGM13 is added to TCCR1B.

The16-bit Timer/Counterhas improvements that will affectthe compatibility in some

specialcases.

Table 49. Definitions

BOTTOM The counterreaches the

BOTTOM

when it becomes 0x0000.

MAX The counterreaches its

MAX

imum when it becomes 0xFFFF (decimal

65535).

TOPThe counterreaches the

TOP

when it becomes equal to the highest

value in the count sequence. TheTOPvalue can beassigned to beone

of the fixed values: 0x00FF, 0x01FF, or 0x03FF, or to thevalue stored in

the OCR1A orICR1 Register.Theassignment isdependent of themode

of operation.

1 2 ... 91 92 93 94 95 96 97 98 99 100 101 ... 222 223

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