Analog MUX Can Be Turned Off When Setting the ACME Bit

If the ACME (Analog Comparator Multiplexer Enabled) bit in ADCSRB is set while MUX3 in ADMUX is ‘1’ (ADMUX[3:0]=1xxx), all MUXs are turned off until the ACME bit is cleared.

Work around

Clear the MUX3 bit before setting the ACME bit.

Affected Silicon Revisions

ATmega48A/PA
Rev. D Rev. E
X X
ATmega88A/PA
Rev. F Rev. G
X X
ATmega168A/PA
Rev. E Rev. L
X X
ATmega328/P
Rev. A Rev. B Rev. D
X X X