Rainbow-electronics ATmega8515L Uživatelský manuál stáhnout pdf (Strana 77)

ATmega8515(L)

2512A–AVR–04/02

8-bit Timer/Counter0

with PWM

Timer/Counter0is ageneralpurpose,single channel, 8-bit Timer/Counter module. The

main features are:

•

Single Channel Counter

• Clear Timer on Compare Match (Auto Reload)

• Glitch-free, Phase Correct Pulse Width Modulator (PWM)

• Frequency Generator

• External Event Counter

• 10-bit Clock Prescaler

• Overflow and Compare Match Interrupt Sources (TOV0 and OCF0)

Overview A simplifiedblock diagram of the8-bit Timer/Counter isshowninFigure 33. For the

actualplacement ofI/Opins, refer to “Pinout ATmega8515” on page 2. CPU accessible

I/O Registers, including I/Obits andI/Opins, are showninbold.The device-specificI/O

page 87.

Figure 33. 8-bit Timer/CounterBlock Diagram

Registers TheTimer/Counter(TCNT0) andOutput CompareRegister(OCR0) are8-bit registers.

Interrupt request (abbreviated to Int.Req.inthe figure)signals areall visibleintheTimer

Interrupt Flag Register(TIFR).All interrupts areindividually maskedwith theTimer

Interrupt Mask Register(TIMSK).TIFRand TIMSK are not showninthe figure since

these registers are sharedbyother timer units.

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

sourceontheT0pin. The Clock Select logicblock controls which clock sourceand edge

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

Timer/Counter

DATA B U S

TCNTn

Waveform

Generation

OCn

= 0

Control Logic

0xFF

BOTTOM

count

clear

direction

TOVn

(Int.Req.)

OCRn

TCCRn

Clock Select

Edge

Detector

( From Prescaler )

clk

TOP

OCn

(Int.Req.)

1 2 ... 72 73 74 75 76 77 78 79 80 81 82 ... 222 223

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