The voltages should be obvious. Your processor has a corresponding datasheet. It will tell about output voltages, unless you load the outputs too hard.

But the timing is another issue. Don't rely on C code if you need to count clock cycles. Different compilers and different optimization levels will produce different code.

Your assign of low and high are directly after each other so maybe no surprises there. But then think about the loop code that decrements a 16-bit (at least) variable before deciding to take another turn. We can guess at possible assembly code for that, but there is no way we can know for sure without actually compiling and then disassembling the generated code.