Sources for STM8(need some changes in power on behaviour)

Hello. I’m using VIM3L
I need some changes in power on behaviour. I don’t need automatic boot when power is connected. Where can I find sourcecode for STM8 to fix it?
Or is any other way to fix it? Of course I can hold reset pin on STM8 with external MCU and it will not start, but I don’t like this method.

@ancc78 We are not open to the source code of MCU.What modifications do you need to make to power management?

I don’t need automatic boot, when power is connected.
I need boot only by pressing the “power” button.