Difference Between Parallel Port and Serial Port and Common Types of Serial Port

Parallel interface

A parallel interface called a parallel port. The parallel port uses a 25-pin D-type connector. The so-called "parallelism" refers to simultaneous transmission of 8-bit data on parallel lines, which greatly improves data transfer rate, but length of parallel transmission lines is limited because length increases, noise increases, and data is error prone. At present, parallel interface is mainly used as a printer port and like.

Parallel port mode:

SPP, called standard parallel port, in English: standard parallel port, this is first working mode of parallel port, almost all peripheral devices using parallel port support this mode.

EPP, called Enhanced High Speed ​​Parallel Port, in English: Enhanced Parallel Port, is a new operating mode developed from SPP. This is also most widely used parallel port mode of operation. Currently, most printers and scanners on market support EPP mode.

ECP stands for Extended Capability Parallel Port, in English: ExtendedCapability Port. This is currently a relatively advanced mode of operation for parallel port, but there are other compatibility issues. Do not select this mode if peripheral device does not support ECP mode.

Serial port

A serial port is called a serial port, also known as a serial communications interface, that is, a COM port. According to electrical standards and protocols, these include RS-232-C, RS-422, RS485, USB, etc. RS-232-C, RS-422 and RS-485 standards define only electrical characteristics of interface and do not apply to connectors, cables or protocols. USB is a new interface standard developed in recent years, mainly used in field of high-speed data transmission.

1

RS-232-C

RS-232-C is also known as standard serial port, which is currently most commonly used serial communication interface. It is a serial communication standard established in 1970 by Electronic Industries Association (EIA) and Bell Systems, a manufacturer of modems and computer terminals. Its full name is "Technical Standard for Serial Binary Data Interchange for Data Communication Equipment (DTE) and Data Communication Equipment (DCE)".

The traditional RS-232-C interface standard has 22 wires and uses a standard 25-pin D-type socket. Later PCs used a simplified 9-pin D-type connector. 25-pin sockets are rarely used in applications these days. Modern computers usually have two serial ports: COM1 and COM2. You can see 9-pin D-type connector on back of computer. Today, many data cables for mobile phones or logistic receivers are connected to computers via COM ports.

2

RS-422

To remedy shortcomings of RS-232 related to short communication distance and low speed, RS-422 defines a balanced communication interface that increases transmission rate to 10 Mbps and transmission distance. up to 4000 feet (slow and over 100 kbps), and up to 10 receivers can be connected to a balanced bus. RS-422 is a one-way balanced transmission specification for single-machine transmission and multi-machine reception, known as TIA/EIA-422-A standard.

3

RS-485

To expand its scope, EIA formulated RS-485 standard based on RS-422 in 1983, adding multipoint and two-way communication functionality that allows multiple transmitters to communicate. on same bus. Transmitter driveability and fault protection were improved, and common mode bus range, later known as TIA/EIA-485-A standard, was extended.

4

USB

Universal Serial Bus, USB for short, is a new type of bus created by several major manufacturers such as Intel, Microsoft, Compaq, IBM, NEC, and Northern Telcom. standard device interface. The USB connector is a four-pin connector on computer motherboard. The two pins in middle carry data, while two pins on sides provide power to peripherals.

The USB interface is fast, easy to connect, no external power supply is required, transfer rate is 12Mbps, and latest version of USB 2.0 can reach 480Mbps; maximum cable length is 5 meters, and USB cable is 4 wires, 2 signalwires and 2 wires. The power cord can supply 5V power, and USB cable is divided into shielded and unshielded. The shielded cable transmission speed can reach 12Mbps, and price is higher. Unshielded cables are good at 1.5 Mbps, but they are cheaper. USB can connect up to 127 devices in series, supports hot plug function.

5

RJ45

The RJ45 interface is most commonly used interface for Ethernet. RJ45 is a generic name that refers to a module standardized by IEC(60)603-7 and uses 8 positions (8 pins) as defined by international connector standard. Modified connector or plug.

6

Switch Serial Port

The switch's serial port in English is trunk; it is used to transform routing of next hop. Each VLAN can only be connected to an external network after being routed to backbone.

Difference between serial port and parallel port

A serial port is described as a channel, while a parallel port means there are 8 channels that can transfer 8 bits (one byte) of data at a time.

But it's not parallel fast due to mutual interference between 8-bit tracks. The speed is limited during transmission. And, when a transmission error occurs, 8-bit data must be re-transmitted at same time. The serial port doesn't interfere, it just forwards a bit after a transmission error. Hence, it is faster than parallel processing. Serial hard drives are valued in this way.