AT43USB355 datasheet(45/115 Pages) ATMEL

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AT43USB355

2603G–USB–04/06

Timer/Counter1 Control Register B – TCCR1B

•Bit 7 – ICNC1: Input Capture1 Noise Canceler (4 CKs)

When the ICNC1 bit is cleared (zero), the input capture trigger noise canceler function is dis-

abled. The input capture is triggered at the first rising/falling edge sampled on the ICP (input

capture pin) as specified. When the ICNC1 bit is set (one), four successive samples are mea-

sured on the ICP and all samples must be high/low according to the input capture trigger

specification in the ICES1 bit. The actual sampling frequency is the 12 MHz system clock

frequency.

•Bit 6 – ICES1: Input Capture1 Edge Select

While the ICES1 bit is cleared (zero), the Timer/Counter1 contents are transferred to the Input

Capture Register (ICR1) on the falling edge of the ICP. While the ICES1 bit is set (one), the

Timer/Counter1 contents are transferred to the ICR1 on the rising edge of the ICP.

• Bits 5, 4 – Res: Reserved Bits

These bits are reserved bits in the AT43USB355 and always read zero.

•Bit 3 – CTC1: Clear Timer/Counter1 on Compare Match

When the CTC1 control bit is set (one), the Timer/Counter1 is reset to $0000 in the clock cycle

after a compareA match. If the CTC1 control bit is cleared, Timer/Counter1 continues counting

and is unaffected by a compare match. Since the compare match is detected in the CPU clock

cycle following the match, this function will behave differently when a prescaling higher than 1

is used for the timer. When a prescaling of 1 is used, and the compareA register is set to C,

the timer will count as follows if CTC1 is set:

... | C-2 | C-1 | C | 0 | 1 | ...

When the prescaler is set to divide by 8, the timer will count like this:

... | C-2, C-2, C-2, C-2, C-2, C-2, C-2, C-2 | C-1, C-1, C-1, C-1, C-1, C-1, C-1, C-1 | C, 0, 0, 0,

0, 0, 0, 0 | ...

In PWM mode, this bit has no effect.

• Bits 2, 1, 0 – CS12, CS11, CS10: Clock Select1, Bit 2, 1 and 0

The Clock Select1 bits 2, 1 and 0 define the prescaling source of Timer/Counter1.

Bit

543

$2E ($4E)

ICNC1

ICES1

–

CTC1

CS12

CS11

CS10

TCCR1B

Read/Write

R/W

Initial Value

Table 14. Clock 1 Prescale Select

CS12

CS11

CS10

Description

Stop, the Timer/Counter1 is stopped.

001

010

CK/8

011

CK/64

100

CK/256

AT43USB355 Scheda tecnica(PDF) 45 Page - ATMEL Corporation

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