Rainbow Electronics ATmega3290P_V - Manual (Page 365)

365
ATmega329/3290/649/6490
2552H–AVR–11/06
ATmega3290 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
Register, OCR2.
ATmega3290 rev. B
Not sampled.
ATmega3290 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
CC
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
Register, OCR2.