Input and output devices I/O device summary

 I/O devices are also called input and output devices.

As shown in the figure above, the I/O bus includes the data bus, control bus, and address bus;

Each I/O device is connected to the I/O bus to transmit data with the PC. Therefore, the concept of I/O interface was derived, and gradually a technology "I/O interface technology" was generated.

The I/O interface circuit is located between the CPU and the peripherals (complex peripherals require a device controller). The peripherals transmit information to the microprocessor for processing through the I/O interface, and the microprocessor transmits the processed information to the peripherals through the I/O interface.

A typical I/O interface should include: port, address decoding, bus driver, and control logic.

I/O ports are registers that the CPU can directly access, including status registers, data registers, and control registers.

Address decoding is the process of decoding the address of the I/O bus to select the I/O port.

The bus driver is a "three-state gate" between the I/O port and the I/O bus, which realizes the "floating" and "connection" between the CPU and the I/O interface.

The control logic receives information from the control port and controls the operation of the interface.

(The above black text belongs to the textbook definition, which may be different from understanding the Linux kernel. It is for reference only)

The I/O bus is connected to the I/O port and register group through the bus driver (three-state), interprets the signal through the I/O interface, sends it to the device controller for further interpretation, converts it into appropriate electrical signals, and controls the corresponding operation of the peripheral.

The reverse operation works in the same way.

I/O interface is divided into dedicated interface and general interface.

Dedicated I/O interface: dedicated to a specific hardware device. For example: graphics interface, network interface (packaged with the controller in the network card, which can receive and send network messages).

A universal I/O interface used to connect multiple different hardware devices, such as parallel port (printer), serial port (UART), SCSI port, and universal serial bus (USB).

Complex devices may require a device controller to drive them. The two important functions of the controller refer to the text in understanding the Linux kernel.

Simpler devices, such as interrupt controllers and timers, do not require secondary parsing and level conversion of high-level instructions of the I/O interface, so they do not require a device controller.

I/O devices are generally divided into character devices and block devices.