ATMEGA64L-8MI View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATMEGA64L-8MI

8-bit AVR® Microcontroller with 64K Bytes In-System Programmable Flash

Atmel Corporation 

• Bit 0 – TOV0: Timer/Counter0 Overflow Flag

The bit TOV0 is set (one) when an overflow occurs in Timer/Counter0. TOV0 is cleared

by hardware when executing the corresponding interrupt handling vector. Alternatively,

TOV0 is cleared by writing a logic one to the flag. When the SREG I-bit, TOIE0

(Timer/Counter0 Overflow Interrupt Enable), and TOV0 are set (one), the

Timer/Counter0 Overflow interrupt is executed. In PWM mode, this bit is set when

Timer/Counter0 changes counting direction at 0x00.

Timer/Counter Prescaler Figure 45. Prescaler for Timer/Counter0

clkOSC

TOSC1

clkT0S

Clear

10-BIT T/C PRESCALER

AS0

PSR0

0

CS00

CS01

CS02

TIMER/COUNTER0 CLOCK SOURCE

clkT0

The clock source for Timer/Counter0 is named clkT0S. clkT0S is by default connected to

the main system clock clkOSC. By setting the AS0 bit in ASSR, Timer/Counter0 is asyn-

chronously clocked from the TOSC1 pin. This enables use of Timer/Counter0 as a Real

Time Counter (RTC). When AS0 is set, pins TOSC1 and TOSC2 are disconnected from

Port C. A crystal can then be connected between the TOSC1 and TOSC2 pins to serve

as an independent clock source for Timer/Counter0. The Oscillator is optimized for use

with a 32.768 kHz crystal. Applying an external clock source to TOSC1 is not

recommended.

For Timer/Counter0, the possible prescaled selections are: clkT0S/8, clkT0S/32, clkT0S/64,

clkT0S/128, clkT0S/256, and clkT0S/1024. Additionally, clkT0S as well as 0 (stop) may be

selected. Setting the PSR0 bit in SFIOR resets the prescaler. This allows the user to

operate with a predictable prescaler.

108 ATmega64(L)

2490G–AVR–03/04

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