Curiosity on how Touch ID work

[naruto55]

As we know, the Touch ID on iPhone 5s is incredible be used to unlock the phone. However, I have a question that how actually Touch ID actually work (as I do not have iPhone 5s right now).

When the phone sleep, can we just tab on Touch ID (without actually clicking on home button) and the phone will wake up and unlock by itself or we have to click on home button to wake the phone up first then tab our finger on Touch ID to unlock it.

It is kind of ridiculous question but for me, as conservative person (too much conservative sometimes), I want to keep the home button as long as possible.

 

[viewfly]

If the phone is completely locked and screen off, one click will wake the phone up and read your fingerprint at the same time

If the screen is already awake, but phone locked, perhaps by using top button to wake phone, then there is only need to touch sensor to unlock. Clicking the home button is not necessary.