Micros equal multiple of four?

Projects Programming
1

I saw this infos on the reference;

http://arduino.cc/en/Reference/Micros

Returns the number of microseconds since the Arduino board began running the current program. This number will overflow (go back to zero), after approximately 70 minutes. On 16 MHz Arduino boards (e.g. Duemilanove and Nano), this function has a resolution of four microseconds (i.e. the value returned is always a multiple of four). On 8 MHz Arduino boards (e.g. the LilyPad), this function has a resolution of eight microseconds.
Note: there are 1,000 microseconds in a millisecond and 1,000,000 microseconds in a second.

so the time time that the board returns is always a multiple of four?
so four example it returns 20000 how much it is actually

2

john191498:
I saw this infos on the reference;

http://arduino.cc/en/Reference/Micros

Returns the number of microseconds since the Arduino board began running the current program. This number will overflow (go back to zero), after approximately 70 minutes. On 16 MHz Arduino boards (e.g. Duemilanove and Nano), this function has a resolution of four microseconds (i.e. the value returned is always a multiple of four). On 8 MHz Arduino boards (e.g. the LilyPad), this function has a resolution of eight microseconds.
Note: there are 1,000 microseconds in a millisecond and 1,000,000 microseconds in a second.

so the time time that the board returns is always a multiple of four?
so four example it returns 20000 how much it is actually

20000 +/- 2. Next time it will return 20004 +/- 2

3

So if you can read it every microsecond, you will get 20000,20000,20000,20000,20004,20004,20004,20004,20008... The clock can not resolve time less than 4 microseconds but the reading IS in microseconds.

4

The prescaler for the timer (timer 0) is set to 64 so it ticks every 64 * 62.5 nS which is 4000 µS. 4000 nS (4 µS).

micros () then multiplies by a suitable number (4, presumably, in effect) to return microseconds (however, only accurate to the nearest 4 of them).

You can time to 62.5 nS precision if you set up your own timer (eg. timer 1).