AT90SCR100 datasheet(150/433 Pages) ATMEL

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TPR0327AY–SMS–30Jan09

AT90SCR100

13.3.8.4

OCR2A – Output Compare Register A

The Output Compare Register A contains an 8-bit value that is continuously compared with the

counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to

generate a waveform output on the OC2A pin.

13.3.8.5

OCR2B – Output Compare Register B

The Output Compare Register B contains an 8-bit value that is continuously compared with the

counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to

generate a waveform output on the OC2B pin.

13.3.9

Asynchronous operation of the Timer/Counter

13.3.9.1

ASSR – Asynchronous Status Register

• Bit 6 – EXCLK: Enable External Clock Input

When EXCLK is written to one, and asynchronous clock is selected, the external clock input buf-

fer is enabled and an external clock can be input on Timer Oscillator 1 (TOSC1) pin instead of a

32 kHz crystal. Writing to EXCLK should be done before asynchronous operation is selected.

Note that the crystal Oscillator will only run when this bit is zero.

• Bit 5 – AS2: Asynchronous Timer/Counter2

When AS2 is written to zero, Timer/Counter2 is clocked from the I/O clock, clkI/O. When AS2 is

written to one, Timer/Counter2 is clocked from a crystal Oscillator connected to the Timer Oscil-

lator 1 (TOSC1) pin. When the value of AS2 is changed, the contents of TCNT2, OCR2A,

OCR2B, TCCR2A and TCCR2B might be corrupted.

• Bit 4 – TCN2UB: Timer/Counter2 Update Busy

When Timer/Counter2 operates asynchronously and TCNT2 is written, this bit becomes set.

When TCNT2 has been updated from the temporary storage register, this bit is cleared by hard-

ware. A logical zero in this bit indicates that TCNT2 is ready to be updated with a new value.

• Bit 3 – OCR2AUB: Output Compare Register2 Update Busy

Bit

$0000B3

OCR2A [7..0]

OCR2A

Read/write

R/W

Initial value

0x00

Bit

$0000B4

OCR2B [7..0]

OCR2B

Read/write

R/W

Initial value

0x00

Bit

654

$0000B6

EXCLK

AS2

TCN2UB

OCR2AUB OCR2BUB TCR2AUB

TCR2BUB

ASSR

Read/write

R/W

Initial value

0x00

AT90SCR100 Datasheet(PDF) 150 Page - ATMEL Corporation

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