The fair, a good simulation is not an easy thing. There are thousands of different microcontroller, are all different. But there is no need to simulate each microcontroller-specific thing, that would otherwise seem impossible.

The basic 8051 and 8052 functions, the program can simulate. But I do not see the point, for example, the SPI simulation. Nothing to connect, there will be no data transfer. The same applies for example to the A/D conversion.

But the compiler and the simulator is capable of handling the special registers, but the simulator does not do anything, when the register contents are changed.

If you do not choose a microcontroller for your model, you can easily create it.
I apologize, but I have not had time to write the user manual.
If you need further assistance, I can welcome help you, contact me by e-mail: http://turbo51studio.orgfree.com/contact.html

Zoltan