Rainbow-electronics ATmega8515L Manual de usuario descargar pdf (Pagina 95)

ATmega8515(L)

2512A–AVR–04/02

Figure 46. 16-bit Timer/CounterBlock Diagram

(1)

Note: 1. Refer to Figure1onpage 2, Table29 on page 64, and Table 35onpage 69 for

Timer/Counter1 pin placement anddescription.

Registers The

Timer/Counter

(TCNT1),

Output Compare Registers

(OCR1A/B), and

Input Capture

(ICR1) areall 16-bit registers. Specialprocedures must be followedwhen

accessing the16-bit registers.These procedures are described in the section “Access-

ing 16-bit Registers”onpage 97.The

Timer/Counter Control Registers

(TCCR1A/B) are

8-bit registers andhave no CPU access restrictions. Interrupt requests(abbreviated to

Int.Req.inthe figure)signals areall visibleinthe

Timer Interrupt Flag Register

(TIFR).

All interrupts areindividually maskedwith the

Timer Interrupt Mask Register

(TIMSK).

TIFRand TIMSK arenotshowninthe figure sincethese registers are sharedbyother

timer units.

TheTimer/Countercan be clocked internally, via the prescaler, orbyan externalclock

sourceontheT1pin. The Clock Select logicblock controls which clock sourceand edge

theTimer/Counter uses to increment (ordecrement) its value. TheTimer/Counter is

inactive when no clock sourceisselected.Theoutput from the clock select logic is

referred to as thetimerclock (clk

The double bufferedOutput CompareRegisters (OCR1A/B) are comparedwith the

Timer/Counter value at all time. The resultof the compare can beusedbythe waveform

generator to generate a PWM or variable frequency output on the Output ComparePin

(OC1A/B). See “Output Compare Units”onpage 103.The comparematch event will

Clock Select

Timer/Counter

DATA BUS

OCRnA

OCRnB

ICRn

TCNTn

Waveform

Generation

Waveform

Generation

OCnA

OCnB

Noise

Canceler

ICPn

Fixed

TOP

Values

Edge

Detector

Control Logic

TOP BOTTOM

Count

Clear

Direction

TOVn

(Int.Req.)

OCnA

(Int.Req.)

OCnB

(Int.Req.)

ICFn (Int.Req.)

TCCRnA TCCRnB

( From Analog

Comparator Ouput )

Edge

Detector

( From Prescaler )

clk

1 2 ... 90 91 92 93 94 95 96 97 98 99 100 ... 222 223

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