What is the role and function of the controller?

The function of the controller in this paper refers to the controller in the computer. Firstly, the controller (English name: controller) refers to changing the wiring of the main circuit or the control circuit according to a predetermined order and changing the resistance value in the circuit to control the starting of the motor. Main control for speed regulation, braking and reverse. It consists of a program counter, an instruction register, an instruction decoder, a timing generator, and an operation controller. It is a "decision-making body" that issues commands, that is, completes the operation of coordinating and directing the entire computer system.

The role of the controller

It controls and coordinates the actions of the entire computer. Controls typically require a program counter (PC), an instruction register (IR), an instruction decoder (ID), timing and control circuitry, and pulse sources, interrupts, and the like. The controller is composed of: an instruction register Instruction Register, an instruction decoder Instruction Decoder, a timing and control circuit Programmable Logic Array, a program counter Program Counter, a flag register Flags Register, a stack and a stack pointer Stack Pointer, a register set, and the like.

Controller function

Data buffering: Due to the low rate of I/O devices and the high rate of CPU and memory, a buffer must be set in the controller. At the time of output, this buffer temporarily stores the data transmitted by the host at high speed, and then transfers the data in the buffer to the I/O device at the rate of the I/O device; at the time of input, the buffer uses After temporarily storing the data sent from the I/O device, after receiving a batch of data, the data in the buffer is transmitted to the host at high speed.

Error Control: The device controller also handles error detection of data transmitted by the I/O device. If an error occurs during transmission, the error detection code is usually set and reported to the CPU, so the CPU invalidates the data transmitted this time and retransmits it. This will ensure the correctness of the data input.

Data exchange: This refers to the exchange of data between the CPU and the controller and between the controller and the device. For the former, data is written to the controller in parallel by the CPU through the data bus, or data is read out in parallel from the controller; for the latter, the device inputs data to the controller or from the controller to the device. . To do this, the data register must be set in the controller.

Status Description: The status controller of the identification and reporting device should note the status of the device for the CPU to understand. For example, the CPU can start the controller to read data from the device only when the device is in the ready state. To this end, a status register should be set in the controller, with each of them reflecting a certain state of the device. When the CPU reads in the contents of the register, you can know the status of the device.

Receive and recognize commands: The CPU can send a variety of different commands to the controller, and the device controller should be able to receive and recognize these commands. To this end, there should be a corresponding control register in the controller to store the received commands and parameters and to decode the received commands. For example, the disk controller can receive 15 different commands such as Read, Write, and Format sent by the CPU, and some commands also have parameters; accordingly, there are multiple registers and command decoders in the disk controller.

Address recognition: Just as every cell in memory has an address, every device in the system also has an address, and the device controller must be able to identify the address of each device it controls. In addition, in order for the CPU to write (or read) data to (or from) registers, these registers should have unique addresses.