Rainbow-electronics ATmega3290P_V Manual do Utilizador descarregar pdf (Página 364)

364

ATmega329/3290/649/6490

2552H–AVR–11/06

Errata

ATmega329 rev. C

• Interrupts may be lost when writing the timer registers in the asynchronous timer

1. Interrupts may be lost when writing the timer registers in the asynchronous

timer

If one of the timer registers which is synchronized to the asynchronous timer2 clock

is written in the cycle before a overflow interrupt occurs, the interrupt may be lost.

Problem Fix/Wortkaround

Always check that the Timer2 Timer/Counter register, TCNT2, does not have the

value 0xFF before writing the Timer2 Control Register, TCCR2, or Output Compare

ATmega329 rev. B

Not sampled.

ATmega329 rev. A

• LCD contrast voltage too high

• Interrupts may be lost when writing the timer registers in the asynchronous timer

1. LCD contrast voltage too high

When the LCD is active and using low power waveform, the LCD contrast voltage

can be too high. This occurs when V

is higher than V

LCD

, and when using low

LCD drivetime.

Problem Fix/Workaround

There are several possible workarounds:

- Use normal waveform instead of low power waveform

- Use drivetime of 375 µs or longer

2. Interrupts may be lost when writing the timer registers in the asynchronous

timer

If one of the timer registers which is synchronized to the asynchronous timer2 clock

is written in the cycle before a overflow interrupt occurs, the interrupt may be lost.

Problem Fix/Wortkaround

Always check that the Timer2 Timer/Counter register, TCNT2, does not have the

value 0xFF before writing the Timer2 Control Register, TCCR2, or Output Compare

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Rainbow-electronics ATmega3290P_V Manual do Utilizador Página 364