Main classification of controller
The controller is divided into a combination of a logic controller and a microprogram controller, each of which has strengths and weaknesses. The combinational logic controller is cumbersome to design and has a complicated structure. Once the design is completed, it cannot be modified or expanded, but it is fast. The microprogram controller is easy to design, simple in structure, convenient to modify or expand, and to modify the function of a machine instruction, only need to reprogram the corresponding microprogram; to add a machine instruction, just add a micro program in the control memory. However, it is done by performing a shred. The specific comparison is as follows: The combination logic controller, also known as the hard wiring controller, is composed of logic circuits, and the functions of the instructions are completely realized by hardware.