Because once you apply for a patent, your invention will be made public, and if someone else uses the content of your patent application in the single chip microcomputer, it is difficult for you to find it, and even if you find it, it is difficult to prove that others have infringed.
Therefore, if you want to apply for a patent for a single-chip computer program, it is best that your program corresponds to some observable phenomenon, that is, if there is some phenomenon in someone else's system, you can prove that your program must have been used.
There is no need for a program with a single chip microcomputer in the patent specification, as long as the implementation method is explained. The patent application is finally written by a lawyer or patent agent.