Rainbow-electronics ATmega161L Manual do Utilizador descarregar pdf (Página 44)

ATmega161(L)

1228C–AVR–08/02

Timer Counter0 – TCNT0

Timer/Counter2 – TCNT2

These 8-bit registers contain the value of the Timer/Counters.

Both Timer/Counters are realized as up or up/down (in PWM mode) counters with read

and write access. If the Timer/Counter is written to and a clock source is selected, it con-

tinues counting in the timer clock cycle following the write operation.

Timer/Counter0 Output

Compare Register – OCR0

Timer/Counter2 Output

Compare Register – OCR2

The Output Compare Registers are 8-bit read/write registers. The Timer/Counter Output

Compare Registers contain the data to be continuously compared with the

Timer/Counter. Actions on compare matches are specified in TCCR0 and TCCR2. A

software write to the Timer/Counter Register blocks compare matches in the next

Timer/Counter clock cycle. This prevents immediate interrupts when initializing the

Timer/Counter.

A compare match will set the Compare Interrupt Flag in the CPU clock cycle following

the compare event.

Timer/Counters 0 and 2 in

PWM Mode

When PWM mode is selected, the Timer/Counter either wraps (overflows) when it

reaches $FF or it acts as an up/down counter.

If the up/down mode is selected, the Timer/Counter and the Output Compare Registers

(OCR0 or OCR2) form an 8-bit, free-running, glitch-free and phase-correct PWM with

outputs on the PB0(OC0/PWM0) or PB1(OC2/PWM2) pin.

If the Overflow mode is selected, the Timer/Counter and the Output Compare Registers

(OCR0 or OCR2) form an 8-bit, free-running and glitch-free PWM, operating with twice

the speed of the up/down counting mode.

Bit 76543210

$32 ($52) MSB LSB TCNT0

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$23 ($43) MSB LSB TCNT2

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$31 ($51) MSB LSB OCR0

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$22 ($42) MSB LSB OCR2

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

InitialValue00000000

1 2 ... 39 40 41 42 43 44 45 46 47 48 49 ... 158 159

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