Papabravo 
The Mandarins at Atmel have made a serious error on Revision U of the ATmega128 datasheet. The diagram of Timer0 is different than the one from Revision S. of the same datasheet. TCCR0 now apparently allows clocking on rising and falling edges of pin T0. Problem is there is no pin T0 on an ATmega128.
Looks like some kind of cut and paste kerfuffle, and of course the real part does not match Revision U. of the datasheet.
I'm sticking with Revision S., Don't know about Rev T.
theusch 
Consider adding the information to the sticky post about unpublished errata.
It's interesting that Atmel would make substantial changes to a "mature" model's datasheet.
There doesn't seem to be anything directly on this in the Datasheet Revision History, unless it is under the catch-all "3. Updated use of Technical Terminology in datasheet".
It certainly appears to be a cock-up, as there are references to timer0 in the timer2 chapter as well.
Lee
Papabravo You can just imagine my panic yesterday when an obscure Timer0 problem cropped up in some mature firmware and I went to the Revision U datasheet and found to my horror that my #define constants were WRONG!, and had been for some time?!?!
I ended up implementing a simple Timer0 Overflow interrupt to toggle an unused pin so I could measure the result, and confirmed that the Revision S. datasheet and my #defines were correct.
I will try to add this discovery to the appropriate Sticky.
theusch
I will try to add this discovery to the appropriate Sticky.
Lee
wek There is a V revision out there.
http://www.atmel.com/dyn/resourc...
I did not check, what's changed.
JW
theusch
I did not check, what's changed.
Datasheet Revision History
Rev. 2467V-02/111. Updated the literature number (2467) that accidently changed in rev U.
2. Editing update according to the Atmel new style guide. No more space betweeen the
numbers and their units.
3. Reorganized the swapped chapters in rev U: 8-bit Timer/Counter 0, 16-bit TC1 and
TC3, and 8-bit TC2 with PWM.
