External interface collection

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External interface collection

Friends who are new to computers often feel overwhelmed by the densely packed interfaces and a large number of connecting cables on the back of the computer;
friends who have been using computers for a long time sometimes want to come up with some small ideas, but often cannot find the pin definitions of various interfaces;
if you have the above experience, then this article will surely be of some help to you, that is, a large collection of external interfaces.

1. Nine-pin serial port:
The serial port is one of the main external interfaces of the computer. There are many devices connected through the nine-pin serial port, such as serial mouse, MODEM, handwriting tablet, etc. The schematic diagram of the nine-pin serial port is as follows. The definition of each pin is as follows:
1 DCD Carrier Detect
2 RXD Receive Data
3 TXD Transmit Data
4 DTR Data Terminal Ready
5 SG Signal Ground
6 DSR Data Ready
7 RTS Request to Send
8 CTS Clear to Send
9 RI Ring Indicator

2. 25-pin serial port:
The function of the 25-pin serial port is the same as that of the 9-pin serial port. The 25-pin serial port was used to connect paper tape machines, MODEMs, etc. on early computers, and can be used to exchange data online. Because of its large size and single function, the 25-pin serial port is no longer found on today's motherboards. The pin definitions of the 25-pin serial port are as follows:
1 Unused
2 TXD Send data
3 RXD Receive data
4 RTS Request to send
5 CTS Clear to send
6 DSR Data ready
7 SG Signal ground
8 DCD Carrier detect
9 + Send return
10 Unused
11 - Data send
12-17 Unused
18 + Data receive
19 Unused
20 DTR Data terminal ready
21 Unused
22 RI Ring indication
23 Unused
24 Unused
25 Receive return

3. Parallel port:
The parallel port is a very important external device interface of the computer. The most commonly used device to connect is the printer. In addition, many models of scanners are also connected to the computer through the parallel port. The parallel port is also 25-pin. Unlike the 25-pin serial port, the parallel port has 25 holes, so it is often called a "female head", while the serial port is often called a "male head". The pin definitions of the parallel port are as follows:
1 STROBE Select
2-9 DATA0-DATA7 Data 0-7
10 ACKNLG Confirm
11 BUSY Busy
12 PE Paper out
13 SLCT Select
14 AUTO FEED Automatic line feed
15 ERROR Error
16 INIT Initialization
17 SLCT IN Select input\
18-25 GND Ground

4. Keyboard interface:
I don't need to say much about the importance of keyboard interface. The above pictures show AT keyboard (commonly known as large keyboard) and PS2 keyboard (small keyboard). Nowadays, there are more and more PS2 keyboards on the market, while AT keyboard is becoming a thing of the past. Because the definition of keyboard is similar, they have something in common. The pins are defined as follows:
1. DATA data signal
2. Empty
3. GND ground terminal
4. +5V
5. CLOCK clock
6 empty (only for PS2 keyboard)

5. MODEM interface:
With the development of the Internet, MODEM is becoming more and more popular. MODEM is divided into two types: external and internal. Their interfaces have many similar functions. The figure above shows the interfaces of two types of MODEM. The pin definitions are as follows:
1. Serial port connector: The external MODEM is connected to the serial port of the computer through a serial port adapter cable, so this part is the serial port connector.
2. LINE port: The port with the LINE mark is the telephone line connection port, and the MODEM uses this port to access the Internet.
3. PHONE port: You can connect an ordinary telephone to this port, so that you can use the phone when you are not online. When you are online, the phone will be automatically blocked by the MODEM.
4, 5: MIC and SPEAKER (LINE OUT): MODEMs with voice functions often have this MIC port and SPEAKER port. Plug the MIC and speaker into these two ports, and you can complete the operation of making a hands-free call through the MODEM. Of course, MODEMs without voice functions do not have these two ports.

6. USB interface:
USB interface is an increasingly popular interface mode, because the characteristics of USB interface are very prominent: fast speed, good compatibility, no interruption, serial connection, support for hot plug and so on, so now many printers, scanners, digital cameras, digital cameras, MP3 players, MODEM, etc. have begun to use USB as the interface mode, the USB interface definition is also very simple:
1 +5V
2 DATA- Data-
3 DATA+ Data+
4 GND Ground

8. Monitor VGA plug:
The monitor is of course a very important device. The monitor uses a 15-pin male connector. Because the monitor is a relatively independent electronic device, its connector definition also has many more professional parts. The specific pin definitions are as follows:
1 Red
2 Green
3 Blue
4 Empty
5 Ground
6 Red - Ground
7 Green - Ground
8 Blue - Ground
9 Empty
10 Ground
11 Ground
12 SDA
13 Horizontal Sync
14 Vertical Sync
15 SCL

The above are some of the interfaces we will encounter in our daily use of computers. I hope that after reading this article, you will no longer feel unfamiliar with these interfaces.