controller
What is a controller? What is the English of the controller? Controller (English name: controller) refers to the master device that controls the starting, speed regulation, braking and reversing of the motor by changing the wiring of the main circuit or control circuit and changing the resistance value in the circuit in a predetermined order. It is composed of program counter, instruction register, instruction decoder, timing generator and operation controller. It is the "decision-making body" that issues commands, that is, to coordinate and command the operation of the entire computer system. Main classification of controllers: controllers are divided into combinational logic controllers and microprogrammed controllers, each of which has advantages and disadvantages. The design of the combined logic controller is troublesome and the structure is complex. 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, 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, simply add a microprogram to the control memory. However, it executes a microprogram. The specific comparison is as follows: the combined logic controller, also known as the hardwired controller, is composed of logic circuits and completely relies on hardware to realize the function of instructions. Working principle of the controller: electromagnetic chuck controller: after the AC voltage of 380V is reduced by the transformer, it is rectified by the rectifier to 110V DC, and then enters the chuck through the control device. At this time, the chuck is magnetized, and the reverse voltage circuit is connected during demagnetization, so the controller can achieve demagnetization function. Access controller: the access controller operates in two modes. One is patrol mode, the other is recognition mode. In patrol mode, the controller continuously sends query codes to the reader and receives the reader's reply commands. This mode will remain until the card reader senses the card. When the card reader senses the card, the card reader will respond differently to the controller's patrol command. In this reply command, the card reader will transmit the read sensing card internal code data to the access controller, so that the access controller will enter the identification mode. In the identification mode of the access controller, the access controller analyzes the internal code of the induction card, compares it with the card data stored in the equipment, and implements the subsequent actions. After the access controller completes the action of receiving data, it will send a command to reply to the card reader, so that the card reader can recover. At the same time, the access controller will return to the patrol mode.