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Introduce Of USB Port, Serial Port And Parallel Poart
- Sep 18, 2018 -

Introduction of USB PortUniversal Serial Bus (abbreviation: USB) is a serial bus standard for connecting computer systems and external devices. It is also a technical specification for input and output interfaces, and is widely used in information communication such as personal computers and mobile devices. and extended to photographic equipment, digital TV (set-top boxes), game consoles and other related fields. The latest generation is USB3.1, the transmission speed is 10Gbit/s, the three-stage voltage is 5V/12V/20V, and the maximum power supply is 100W. The new TypeC plug-in is no longer positive and negative.

Operating principle of USB port

USB is an external bus standard that regulates the connection and communication between a computer and an external device. USB interface supports plug and play and hot plug function. USB interface can connect up to 127 peripherals such as a mouse and keyboard. USB was successfully introduced in 1996 after the launch of a combination of Intel and other companies in 1996. It has become a must-have interface for today's computers and a large number of smart devices. The USB version has evolved over the years and has grown to version 3.0. For most engineers, the main obstacles in developing USB2.0 interface products are: to face the complex USB2.0 protocol, to write the driver of the USB device, and to be familiar with the programming of the micro-controller. This requires not only considerable VC programming experience, but also hardware (firmware) programs that can write USB interfaces. So most people gave up developing their own USB products. In order to simplify the complicated problems, Xi'an Datai Electronics specially designed the USB2.0 protocol conversion module. The USB20D module can be thought of as a USB 2.0 protocol converter that converts the computer's USB 2.0 interface into a transparent parallel bus, just like a micro-controller bus. So within a few days you can complete the design of the USB2.0 product.

USB interface

Advantages of USB port:

1.Support hot swapped. It means when the user uses the external device, the user does not need to turn off the camera and then turn on the computer, etc., just directly plugs the USB into use when the computer is working.

2. Easy to carry. Most USB devices are known for being "small, light, and thin". It is convenient for users to carry large amounts of data with them. Of course, the USB hard drive is the first choice.

3. Standards are unified. Commonly used are the hard disk of the IDE interface, the mouse and keyboard of the serial port, and the printer scanner of the parallel port. However, with USB, these application peripherals can be connected to the personal computer with the same standard. At this time, there is a USB hard disk and USB. Mouse, USB printer, etc.

4.Multiple devices can be connected. USB often has multiple interfaces on a personal computer. It can connect several devices at the same time. If you connect a USBHUB with four ports, you can connect it again. Four USB devices, and so on, can be connected. Connect your home device to a personal computer at the same time without any problems (Note: up to 127 devices can be connected)

Introduction of Serial Port

Serial interface is referred to as serial port, also known as serial communication interface or serial communication interface (usually referred to as COM interface). It is an extended interface using serial communication. Serial interface refers to the sequential transmission of data one by one. It is characterized by simple communication lines. As long as a pair of transmission lines can realize two-way communication (you can directly use the telephone line as a transmission line), the cost is greatly reduced. Suitable for long distance communication, but the transmission speed is slow.

Serial port division standard:

Synchronous Serial Interface (SSI) is a commonly used industrial communication interface. .

Asynchronous serial refers to UART (Universal Asynchronous Receiver/Transmitter), universal asynchronous receiving/sending. The UART is a parallel input that becomes a serial output chip, usually integrated on the motherboard. The UART includes a TTL level serial port and an RS232 level serial port. The TTL level is 3.3V, and RS232 is a negative logic level. It defines +5~+12V as low level, while -12~-5V is high level. MDS2710, MDSSD4, EL805, etc. are RS232 interface, EL806 There is a TTL interface.

The serial interface includes RS-232-C, RS-422, RS485, etc. according to electrical standards and protocols. The RS-232-C, RS-422, and RS-485 standards only specify the electrical characteristics of the interface and do not involve connectors, cables, or protocols.

USB To Dual Serial Converter Cable

Difference between serial port and parallel port:

The serial port describes a lane, and the parallel port has 8 lanes that can transmit 8 bits (one byte) of data at the same time. However, it is not that the parallel port is fast. Due to the mutual interference (crosstalk) between the 8-bit channels, the transmission speed is limited and the transmission is prone to errors. The serial ports do not interfere with each other. The parallel port sends a large amount of data at the same time, but it is slower than the serial port. Serial hard drives are like this.

Introduction of the parallel port

Parallel ports generally refer to parallel interfaces. Parallel interface refers to the interface standard that uses parallel transmission to transmit data. From the simplest parallel data registers or dedicated interface integrated circuit chips such as the 8255, 6820, etc., to the more complex SCSI or IDE parallel interfaces, there are dozens. The interface characteristics of a parallel interface can be described in two aspects: 1. The width of the data channel transmitted in parallel, also known as the number of bits transmitted by the interface; 2. The additional interface control line or interaction used to coordinate parallel data transmission The characteristics of the signal. The width of the data can be from 1 to 128 bits or wider, the most common is 8 bits, and 8 data bits can be transmitted at a time through the interface. The most commonly used parallel interface in the computer field is the so-called LPT interface.

DB25 to CN36 IEEE1284 printer cable

Main features of the parallel port:

Parallel interface refers to the simultaneous transmission of data bits, which is characterized by fast transmission speed, but when the transmission distance is long and the number of bits is large, the communication line is complicated and the cost is increased.

Classification of parallel ports:

A variety of parallel interface modes are defined in the IEEE1284 standard. The following three types are commonly used:

SPP (Standard Parallel Port)

EPP (Enhanced Parallel Port)

ECP (Extended Capabilities Port)

These modes can vary from 50KBits/sec to 2MB/sec due to hardware and programming. The interface typically used to transfer data from a host computer to a printer, plotter, or other digital instrument is a 36-pin spring-loaded interface called Centronics (usually a 25-pin D-type connector on the mainframe and a 36-pin Centronics interface on the printer).

DB25 male serial cable