ATmega16 datasheet(107/315 Pages) ATMEL

107 / 315 page

107

ATmega16(L)

2466E–AVR–10/02

Timer/Counter1 Control

• Bit 7 – ICNC1: Input Capture Noise Canceler

Setting this bit (to one) activates the Input Capture Noise Canceler. When the Noise

Canceler is activated, the input from the Input Capture Pin (ICP1) is filtered. The filter

function requires four successive equal valued samples of the ICP1 pin for changing its

output. The input capture is therefore delayed by four Oscillator cycles when the Noise

Canceler is enabled.

• Bit 6 – ICES1: Input Capture Edge Select

This bit selects which edge on the Input Capture Pin (ICP1) that is used to trigger a cap-

ture event. When the ICES1 bit is written to zero, a falling (negative) edge is used as

trigger, and when the ICES1 bit is written to one, a rising (positive) edge will trigger the

capture.

When a capture is triggered according to the ICES1 setting, the counter value is copied

into the Input Capture Register (ICR1). The event will also set the Input Capture Flag

(ICF1), and this can be used to cause an Input Capture Interrupt, if this interrupt is

enabled.

When the ICR1 is used as TOP value (see description of the WGM13:0 bits located in

the TCCR1A and the TCCR1B Register), the ICP1 is disconnected and consequently

the input capture function is disabled.

• Bit 5 – Reserved Bit

This bit is reserved for future use. For ensuring compatibility with future devices, this bit

must be written to zero when TCCR1B is written.

• Bit 4:3 – WGM13:2: Waveform Generation Mode

See TCCR1A Register description.

• Bit 2:0 – CS12:0: Clock Select

The three Clock Select bits select the clock source to be used by the Timer/Counter, see

Figure 49 and Figure 50.

Bit

321

ICNC1

ICES1

–

WGM13

WGM12

CS12

CS11

CS10

TCCR1B

Read/Write

R/W

Initial Value

Table 48. Clock Select Bit Description

CS12

CS11

CS10

Description

No clock source (Timer/Counter stopped).

001

clkI/O/1 (No prescaling)

010

clk

I/O/8 (From prescaler)

011

clk

I/O/64 (From prescaler)

100

clkI/O/256 (From prescaler)

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