Rainbow-electronics ATmega128L Uživatelský manuál stáhnout pdf (Strana 87)

ATmega128(L)

2467B–09/01

8-bit Timer/Counter0 with PWM and Asynchronous Operation

Timer/Counter0 is a general purpose, 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

• 10-bit Clock Prescaler

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

• Allows Clocking from External 32 kHz Watch Crystal Independent of the I/O Clock

Overview A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 33. For the

actual placement of I/O pins, refer to

“Pin Configurations” on page 2. CPU accessible

I/O registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O

“8-bit Timer/Counter Register Description” on

page 98

Figure 33. 8-bit Timer/Counter Block Diagram

Registers The Timer/Counter (TCNT0) and Output Compare Register (OCR0) are 8-bit registers.

Interrupt request (shorten as Int.Req.) signals are all visible in the Timer Interrupt Flag

ister (TIMSK). TIFR and TIMSK are not shown in the figure since these registers are

shared by other timer units.

Timer/Counter

DATAB US

TCNTn

Waveform

Generation

OCn

= 0

Control Logic

= 0xFF

TOPBOTTOM

count

clear

direction

TOVn

(Int.Req.)

OCn

(Int.Req.)

Synchronization Unit

OCRn

TCCRn

ASSRn

Status flags

clk

I/O

clk

ASY

Synchronized Status flags

asynchronous mode

select (ASn)

TOSC1

T/C

Oscillator

TOSC2

Prescaler

clk

I/O

1 2 ... 82 83 84 85 86 87 88 89 90 91 92 ... 330 331

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