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Re: [avr-chat] Differences between ATmega1284 and P version?

From: Rick Mann
Subject: Re: [avr-chat] Differences between ATmega1284 and P version?
Date: Tue, 8 Feb 2011 15:37:46 -0800

On Feb 8, 2011, at 14:48:14, Joerg Wunsch wrote:

> Ruud Vlaming <address@hidden> wrote:
>> i cannot find the datasheet of the 644A, so i have no
>> real comparrisson at the moment.
> I don't think there is any ATmega644A, it's probably only available as
> an ATmega644PA.

There definitely is, I have several in DIP 40, and ordered some in TQFP.

> The ATmega644 vs. ATmega644P is IMHO the only time where the suffix
> letter actually indicated two different feature sets (with/without
> second USART).

The data sheet I have references the following:


Near as I can tell, they all have dual USARTs (that was a requirement for my 

> The "A" devices are die-shrink versions, where all the connections
> have been routed with smaller traces, yet retaining the original
> transistor structure sizes (to avoid different electrical behaviour
> compared to the non-A versions).  This leads to somewhat faster ICs,
> so the original distinction between two speed vs. voltage device
> classes (L/V devices vs. devices without that suffix) became obsolete
> with the A devices.

Thanks for the explanation about "A".

I sure wish they'd have a simple table in each data sheet that covers multiple 
products indicating quickly what aspects are different, and perhaps referencing 
more detailed differences elsewhere.


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