ATMEGA48V_06 ATMEL [ATMEL Corporation], ATMEGA48V_06 Datasheet - Page 362

• Manufacturer Part Number: ATMEGA48V_06
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

- A reset is applied in a 10 ns window while the system clock prescaler value is updated by
software.
- Leaving SPI-programming mode generates an internal reset signal that can trigger this
case.
The two first cases can occur during normal operating mode, while the last case occurs only
during programming of the device.
Problem Fix/Workaround
The first case can be avoided during run-mode by ensuring that only one reset source is
active. If an external reset push button is used, the reset start-up time should be selected
such that the reset line is fully debounced during the start-up time.
The second case can be avoided by not using the system clock prescaler.
The third case occurs during In-System programming only. It is most frequently seen when
using the internal RC at maximum frequency.
If the device gets stuck in the reset-state, turn power off, then on again to get the device out
of this state.
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 writ-
ten in the cycle before an overflow interrupt occurs, the interrupt may be lost.
Problem Fix/Workaround
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.
ATmega48/88/168
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2545J–AVR–12/06