Did you read the Manual for the 328 ?.
The OP is asking about decoupling I'm just trying to inform him of best practice according to ATMEL
WTF, I first wrote that AREF pin indeed can be connected to external voltages (to use them as voltage reference), not just a filtering cap for internal voltage reference. This is explicitly written in the datasheet. You made a counter claim which was false. Now you are writing about some mystical best practices not actually related to AREF pin itself, but about VCC/AVCC. Are the best practices to not use anything other than internal VREF, please explain why? Is this it really recommendation by atmel?
OK perhaps I wasn't clear.
Yes AREF can be connected to an external reference.
I posted that AREF shouldn't really be connected to VCC
The point I was trying to make was that AVCC is the analog supply pin.
So if you must connect it directly to AVCC NOT VCC.
I'm trying to point out that there are separate supply and ground pins for the digital and analog circuits i.e. THE ADC in the MCU.
I've quoted out the page in that manual so it's not a dream.
It really is no different to telling the OP that the decoupling caps should be as close to the pins as possible.
Atmel also state that AVCC can be within I think it was 300mV of VCC
Like I said I'm just trying to inform the OP.
3DB