where does micros() come from ?

Using Arduino Programming Questions
#1

Hi !

trying to have fast loop, I discover that micros() is more than 3micros long to execute. TCNT2 8 bit counter reading about 1.3micros ; TCNT1 16bit 1.44micros.

Where is the "big" counter for micros ?

thx

#2

At least in Arduino AVR Boards, you can find the source code for the function in wiring.c:

#3

pert:
At least in Arduino AVR Boards, you can find the source code for the function in wiring.c:
https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/wiring.c#L79-L104

Thx... It seems that is isr counting of counter 0 overflow ?

#4