The controller is divided into a combination logic controller and a microprogram controller. The controller refers to the master device that changes the wiring of the main circuit or the control circuit and changes the resistance value in the circuit according to a predetermined sequence to control the start, speed, brake, and reverse of the motor.
The combinatorial logic controller (also known as hard-wired controller) is cumbersome to design and has a complicated structure. Once the design is completed, it cannot be modified or expanded. However, it is fast. It is composed of logic circuits and completely relies on hardware to implement instructions.
The microprogram controller is easy to design, simple in structure, and easy to modify or expand. To modify the function of a machine instruction, you only need to reprogram the corresponding microprogram; to add a machine instruction, you only need to add a microprogram to the control memory. However, it does so by executing a micro process.
The basic idea of micro-program control is: use micro-instructions to generate micro-operation commands and use several micro-instructions to form a micro-program to realize the function of a machine instruction. The control memory of the microprogram controller is used to store the microprogram corresponding to each machine instruction. The decoder is used to form the entry address of the microprogram corresponding to the machine instruction.
The width of the microinstruction directly determines the width of the microprogram controller. In order to simplify the control memory, some measures can be taken to shorten the width of the microinstructions.
Combinational logic controllers use combinational logic technology to achieve control operations. The control component is regarded as a logic circuit that generates special fixed timing control signals. This logic circuit is a complex logic network composed of gate circuits and flip-flops.
The control unit is designed with a combinational logic design method. The circuit structure of the micro-operation control component is very complex and irregular, and the more complete the command system function, the more micro-operation commands, the more complicated the circuit. Once the control component is constructed, unless it is redesigned and physically rewired, it is impossible to add new control functions. The biggest advantage of combinatorial logic control is faster speed.