Phase lock loop

Hello to all,
is it possible to program a mikrokontroller to use it with pll to detect the zero coss of the input signal?

does anyone of you have experience with matlab? because matlab have some block diagrams for pll.
another question: is it possible to let simulink to generate the pll blockdiagram in a c code an use the code with a mikrokopntroller?

Is there any specific reason it must be done with PLL? You can do simple zero cross detection with a comparator quite easily. An analog-digital converter module can also be used.

thank you for your help, but i dont want to do it with external parts, only software based.

You don't have to do it with external components. Microcontrollers with on chip comparators exist. Most 8-bit PIC microcontrollers have them. They also have on chip analog-digital converters, which can also do it.