I was reading the arduino documentation and the extended documentation, but the only references i can found about things like timer0_overflow_count or TCNT0 are on the forums and as questions, there isn't documentation about that? i already search on google, but i only find the forums, where should i search?. Thanks.
one of arduino's aim is to provide an easy hardware/software solution, for thing more complex than what's documented in the playground section you should refer to the chip datasheet... ex: for ATmega48PA/88PA/168PA/328P http://www.atmel.com/dyn/resources/prod_documents/doc8161.pdf
While you are reading the documentation mentioned by elwing you might want to look at a diagram that I created while tinkering with the timer. You can find it at http://web.alfredstate.edu/weimandn. Scroll down to the Reference Diagrams link under ‘Atmel ATmega168 Subsystem Diagrams’.
nice diagram.... won't ever replace the datasheet, but it is faster/easier to understand with them...
elwing: you are right, i should read these datasheets. Floresta: your diagrams seems very nice. Many thanks for the fast reply, i will start reading right now.
Also, check out the (relatively) new micros() function for precise timing. You shouldn't need TCNT0 for most things.