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

[Ruud Vlaming]

On Tuesday 08 February 2011, Rick Mann wrote:
> I'm working with the ATmega644A, and I like it, but I could use more memory.
> 
> So I'm looking at the 1284, which comes in a P variant, 
> but no A variant.  I can't figure out what the differences among all 
> these variants are. The 644A comes in a PA variant as well. 
Indeed this P/A business can be confusing. For most chips the
only difference between P en non P is the power consumption
and the possibilty to operate the chips at lower voltages.
A or non A makes much less a difference, usually only
small differences in electrical characteristics. For example:
1284P : V_OLmax (Vcc=5V) 0.7V
644PA:  V_OLmax  (Vcc=5V) 0.9V
i cannot find the datasheet of the 644A, so i have no
real comparrisson at the moment. 

My guess is however that you should be save if you
replace an ATmega644A with an ATmega644PA
or with an ATmega1284P for that matter.
I would in general not replace it the other way around.

One other point of attention: the ATmega1284P used to
have some availability problems, but maybe this is
history by now.

Hope this helps.

Ruud