CPU: Program inside CPU that determines exact principal of instructions (?!)

Question

At Computer Science lecture we've been told that there's a special code (lower that assembler) that determines behavior of CPU which is written inside CPUs ROM. It was meant that is determines what exactly every instruction in boolean logic means… That sounds quite strange – I haven't found any kind of information about that.

Probably he meant not CPU but microcontrollers? But he told that it determines exact behavior of such kind of instructions like MOV, ADD ect. So, I am perplexed.

Or he meant any kind of PCB layout language?

Answer 1

Do you mean microcode?

http://en.wikipedia.org/wiki/Microcode