Serial and parallel port knowledge on electronically connected systems

It is no stranger to electronic products. There are many connection interfaces on the circuit boards and PCB boards used on it. Take the motherboard of the computer as an example. The motherboard of the computer has a VGA port, a DVI port, an HDMI port, a SATA port, an RJ45 network port, a multi-channel audio interface, and a USB mouse and keyboard interface. This article Konnra Electronics engineers mainly introduce you to the serial port and parallel port knowledge on the electronic connection system, mainly in accordance with the three sequences of serial port introduction, parallel port introduction, serial port and parallel port. I hope that after reading this article, you You can have a deeper understanding of the serial port and parallel port on the electronic connection system. 

First, the serial port introduction

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 (SerialInterface) 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.

 

Second, the 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 ways: 

1. The width of the data channel transmitted in parallel, also known as the number of bits transmitted by the interface; 

2. Additional interface control lines or characteristics of interactive signals used to coordinate parallel data transmission. 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. 

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. 

The classification of parallel ports defines a variety of parallel interface modes in the IEEE1284 standard. There are three commonly used ones: 

1.SPP (StandardParallelPort) standard parallel interface; 

2. EPP (Enhanced ParallelPort) enhanced parallel interface; 

3. ECP (ExtendedCapabiliTIesPort) extended function parallel interface. 

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).

 

Third, the 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 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.