The controller refers to the main equipment that changes the wiring of the main circuit control circuit changes the resistance value in the circuit to control the start, speed regulation, braking reverse of the motor in a predetermined sequence. It consists of program counter, instruction register, instruction decoder, timing generator operation controller. It is the "decision-making body" that issues the command, that is, to complete the coordination command of the whole computer system operation.

The controller is divided into combinational logic controller microprogrammed controller, each of which has its own advantages disadvantages. The design of combinational logic controller is complicated complicated. Once the design is completed, it cannot be modified expanded, but it is very fast. Microprogrammed controller is easy to design, simple in structure, easy to modify expand. In order to modify the function of machine instructions, it is only necessary to reprogram the corresponding microprogram; in order to add machine instructions, it is only necessary to add a microprogram in the control memory. However, this is done by executing a micro stroke. The specific comparison is as follows: the combinational logic controller, also known as hardwired controller, is composed of logic circuit completely relies on hardware to realize instruction function.