Rainbow-electronics Atmega169L Manuel d'utilisateur télécharger pdf (Page 95)

ATmega169V/L

2514A–AVR–08/02

Figure 39. 16-bit Timer/Counter Block Diagram

(1)

Note: 1. Refer to Figure 1 on page 2, Table 28 on page 58, and Table 34 on page 62 for

Timer/Counter1 pin placement and description.

Registers The

Timer/Counter

(TCNT1),

Output Compare Registers

(OCR1A/B), and

Input Capture

(ICR1) are all 16-bit registers. Special procedures must be followed when

accessing the 16-bit registers. These procedures are described in the section “Access-

ing 16-bit Registers” on page 97. The

Timer/Counter Control Registers

(TCCR1A/B) are

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

Int.Req. in the figure) signals are all visible in the

Timer Interrupt Flag Register

(TIFR1).

All interrupts are individually masked with the

Timer Interrupt Mask Register

(TIMSK1).

TIFR1 and TIMSK1 are not shown in the figure.

The Timer/Counter can be clocked internally, via the prescaler, or by an external clock

source on the T1 pin. The Clock Select logic block controls which clock source and edge

the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is

inactive when no clock source is selected. The output from the Clock Select logic is

referred to as the timer clock (clk

The double buffered Output Compare Registers (OCR1A/B) are compared with the

Timer/Counter value at all time. The result of the compare can be used by the Waveform

Generator to generate a PWM or variable frequency output on the Output Compare pin

(OC1A/B). See “Output Compare Units” on page 103.. The compare match event will

Clock Select

Timer/Counter

DATA B U S

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 ... 316 317

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Rainbow-electronics Atmega169L Manuel d'utilisateur Page 95

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