ATmega64A datasheet(136/392 Pages) ATMEL

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136

8160C–AVR–07/09

ATmega64A

• Bit 6 – ICESn: Input Capture Edge Select

This bit selects which edge on the Input Capture pin (ICPn) that is used to trigger a capture

event. When the ICESn bit is written to zero, a falling (negative) edge is used as trigger, and

when the ICESn bit is written to one, a rising (positive) edge will trigger the capture.

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

Input Capture Register (ICRn). The event will also set the Input Capture Flag (ICFn), and this

can be used to cause an Input Capture Interrupt, if this interrupt is enabled.

When the ICRn is used as TOP value (see description of the WGMn3:0 bits located in the

TCCRnA and the TCCRnB Register), the ICPn is disconnected and consequently the Input Cap-

ture 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 TCCRnB is written.

• Bit 4:3 – WGMn3:2: Waveform Generation Mode

See TCCRnA Register description.

• Bit 2:0 – CSn2:0: Clock Select

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

15-10 and Figure 15-11.

If external pin modes are used for the Timer/Countern, transitions on the Tn pin will clock the

counter even if the pin is configured as an output. This feature allows software control of the

counting.

15.11.5

TCCR1C – Timer/Counter1 Control Register C

Figure 15-14. Clock Select Bit Description

CSn2

CSn1

CSn0

Description

No clock source (Timer/counter stopped).

001

clk

I/O/1 (No prescaling)

010

clkI/O/8 (From prescaler)

011

clk

I/O/64 (From prescaler)

100

clk

I/O/256 (From prescaler)

101

clkI/O/1024 (From prescaler)

External clock source on Tn pin. Clock on falling edge.

External clock source on Tn pin. Clock on rising edge.

Bit

765

43210

(0x7A)

FOC1A

FOC1B

FOC1C

–––––

TCCR1C

Read/Write

RRRR

Initial Value

000

00000

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