Datasheet

ATmega48/88/168

2545DS–AVR–07/04

Errata ATmega88 The revision letter in this section refers to the revision of the ATmega88 device.

Rev. A • Writing to EEPROM does not work at low Operating Voltages

• Part may hang in reset

1. Writing to EEPROM does not work at low operating voltages

Writing to the EEPROM does not work at low voltages.

Problem Fix/Workaround

Do not write the EEPROM at voltages below 4.5 Volts.

This will be corrected in rev. B.

2. Part may hang in reset

Some parts may get stuck in a reset state when a reset signal is applied when the

internal reset state-machine is in a specific state. The internal reset state-machine is

in this state for approximately 10 ns immediately before the part wakes up after a

reset, and in a 10 ns window when altering the system clock prescaler. The problem

is most often seen during In-System Programming of the device. There are theoreti-

cal possibilities of this happening also in run-mode. The following three cases can

trigger the device to get stuck in a reset-state:

- Two succeeding resets are applied where the second reset occurs in the 10ns win-

dow before the device is out of the reset-state caused by the first reset.

- 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.