How to set breakpoints in the built-in debugger

[VirtualDebugger]

Hello,

I would like to set a breakpoint using the built-in debugger but they are not triggered, e.g. the debugger is not activated.

It's execution on address 0x7c00 right after system start in BIOS that I want to catch and check the loaded boot sector.
So far I tried things like "bp 7c00" or "ba x 1 7c00 stop", also inserting an "int 3h" opcode into my code does not trigger.

Can someone please give me an example, how I can stop and trigger the built-in debugger from my code?

Thanks and best regards