As you all know, most of the 8051 emulation/simulation softwares emulate 8051 Processor architecture.
Is there any such tool, which can append some extra Instructions into the 8051 Processor architecture and do some simulations and debug the codes.
OR,
if there is any method of doing this, you can suggest, without one tool?
One possible solution - which is not an easy one - is to get the code of an open source emulator like this and modify the processor model and the assembler to know your extra instructions. Before you start you should study the processor architecture to know if your modifications are valid or not.