EEAR8 on tiny devices with EEPROM <= 256B

[Ruud Vlaming]

The attiny24/44 have so small an EEPROM that it can be addressed
by one byte, as the manual clearly states, (page 20). Bit EEAR8
is reserved for the ATtiny24/44, so effectively you do not
need EEARH at all for these devices. And it will read zero allways.

A comparable situation exists for the ATtiny25/45 and ATtiny261/461.
These devices also have one byte addressable EEPROMs, but the manuals
suggest (page 20, resp 21) that EEARH must be written nevertheless.

A quick test with the 261/861 seems to indicate that they behave
as if the bit is indeed reserved on the 261, reading of EEAR8
returns a zero, even if a one was written. For the 861 the EEAR8
bit behaves as a memory. But, it could be that this situation
is device specific. In other words, it would not contradict the
current version of the manual, if there are 261 devices out their
that return a one when reading EEAR8. It would not be in line
with their usual policy on reserved bits however.

I did not test all devices, but my primilairy conclusion would
be that the manuals on 261/461/861 and 25/45/85 need to be
updated.

Ruud


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[Weddington, Eric]

 

> -----Original Message-----
> From: avr-chat-bounces+eric.weddington=atmel.com@...
> [mailto:avr-chat-bounces+eric.weddington=atmel.com@...]
>  On Behalf Of Ruud Vlaming
> Sent: Wednesday, September 02, 2009 4:05 AM
> To: avr-chat@...
> Subject: [avr-chat] EEAR8 on tiny devices with EEPROM <= 256B
>
> I did not test all devices, but my primilairy conclusion would
> be that the manuals on 261/461/861 and 25/45/85 need to be
> updated.

Then don't send your message here. Send it to Atmel so the datasheets can be updated.


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[Ruud Vlaming]

On Wednesday 02 September 2009 16:13, you wrote:
 
> > -----Original Message-----
> > I did not test all devices, but my primilairy conclusion would
> > be that the manuals on 261/461/861 and 25/45/85 need to be
> > updated.
>
> Then don't send your message here.

Sorry if i offended you by this posting. But in my view posting here
is adequate because:
(1) I can be wrong with my findings, so before shouting that Atmel
  or anyone else made a mistake i want to give people the oppertunity
  to react possibly correct me.
(2) This information is of general interest, so given the fact that it
  is correct, this is certainly the quickest way to reach other developers.
  After this info has reached the correct person at Atmel it would certainly
  take some time for them to correct the manuals and put it on the net.
(3) It is within scope of this mailinglist

> Send it to Atmel so the datasheets can be updated.
I looked at Atmels website, but saw no obvious channel to route this
information. If you, or anyone else, has an email address i will be
happy to sent it on.

Ruud.




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[Weddington, Eric]

 

> -----Original Message-----
> From: avr-chat-bounces+eric.weddington=atmel.com@...
> [mailto:avr-chat-bounces+eric.weddington=atmel.com@...]
>  On Behalf Of Ruud Vlaming
> Sent: Wednesday, September 02, 2009 9:11 AM
> To: avr-chat@...
> Subject: Re: [avr-chat] EEAR8 on tiny devices with EEPROM <= 256B
>
> On Wednesday 02 September 2009 16:13, you wrote:
>  
> > > -----Original Message-----
> > > I did not test all devices, but my primilairy conclusion would
> > > be that the manuals on 261/461/861 and 25/45/85 need to be
> > > updated.
> >
> > Then don't send your message here.
>
> Sorry if i offended you by this posting.

Sorry, no offense was taken. I did not mean to imply that your message was inappropriate to the list (it's certainly on topic :-). I was just trying to redirect you to a more appropriate place to get the documents changed.

> > Send it to Atmel so the datasheets can be updated.
> I looked at Atmels website, but saw no obvious channel to route this
> information. If you, or anyone else, has an email address i will be
> happy to sent it on.

Sure: avr AT atmel DOT com


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[Ruud Vlaming]

On Wednesday 02 September 2009 18:12, Weddington, Eric wrote:
> > > Send it to Atmel so the datasheets can be updated.
> If you, or anyone else, has an email address i will be happy to sent it on.
> Sure: avr AT atmel DOT com
OK, how easy can life be ;-)
Has been done.
R.





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