What Is a Serial Digital Interface?

The serial interface is referred to as the serial port, which is also called a serial communication interface or a serial communication interface (commonly referred to as a COM interface). It is an extended interface that uses serial communication. Serial interface (Serial Interface) refers to the data transmitted sequentially one by one. Its characteristic is that the communication line is simple, as long as a pair of transmission lines can achieve two-way communication (can directly use the telephone line as a transmission line), which greatly reduces the cost, especially suitable for long-distance communication, but the transmission speed is slow.

Serial

Synchronous Serial Interface (English: SynchronousSerialInterface, SSI) is a commonly used industrial

Serial port of a serial interface switch

The English of the serial port of the switch is trunk; it is used for next hop routing conversion. Each VLAN can access the Internet only after being pointed by the route with TRUNK.

Pin description:

Pin Name Dir Description

1 CD Carrier Detect

2 RXD Receive Data

3 TXD Transmit Data

4 DTR Data Terminal Ready

5 GND System Ground

6 DSR Data Set Ready

7 RTS Request to Send

8 CTS Clear to Send

9 RI Ring Indicator

At present, the more commonly used serial ports are 9-pin serial port (DB9) and 25-pin serial port (DB25). When the communication distance is short (<12m), you can directly connect the standard RS232 port (RS422, RS485) with a cable. Long distance, need to add modem (MODEM) or other related equipment. The simplest and commonly used method is the three-wire connection method, that is, the three-pin connection of ground, receive data, and send data. The following is the most basic connection method, and it is directly connected by RS232.

(1) Description of common signal pins of DB9 and DB25

DB9 | DB25

pin function name pin function name

1 Data carrier detection DCD 8 Data carrier detection DCD

2 Receive data RXD 3 Receive data RXD

3 Send data TXD 2 Send data TXD

4 Data Terminal Preparation DTR 20 Data Terminal Preparation DTR

5 Signal ground GND 7 Signal ground GND

6 Data Device Ready for DSR 6 Data Device Ready for DSR

7 Request to send RTS 4 Request to send RTS

8 Clear Send CTS 5 Clear Send CTS

9 Ring indication RI 22 Ring indication RI

(2) RS232C serial communication connection method (three-wire system)

First, the serial port can transmit data as long as it has a receive data pin and a send pin: the receive pin and the send pin of the same serial port are directly connected by a wire, two serial ports are connected, or one serial port is connected to multiple serial ports.

The receiving pin and the sending pin of the same serial port are directly connected by a wire. The 9-pin serial port and the 25-pin serial port are both directly connected to 2 and 3.

Two different serial ports (whether the two serial ports of the same computer or the serial ports of different computers)

Serial cable

DB9-DB9

2-3,3-2,5-5

DB25-DB25

2-3,3-2,7-7

DB9-DB25

2-3,3-2,5-7

DB9-DB25 serial cable

2-3,3-2,5-7

The above is for the standard serial port of a microcomputer. There are many non-standard devices, such as receiving GPS data or electronic compass data. Just remember one principle: the pin (or line) for receiving data is connected to the pin (or line) for sending data , Cross each other, and the signal grounds correspond to each other.

3. Points to note in serial debugging:

Different coding mechanisms cannot be mixed. For example, RS232C cannot be directly connected to the RS422 interface. Special converters on the market are sold and must be connected through converters.

When serial port debugging, prepare a useful debugging tool, such as serial port debugging assistant, serial port wizard, etc.

It is strongly recommended that you do not plug in or plug in the serial port when it is powered on, otherwise the serial port may be easily damaged.

For large-scale industrial control and measurement equipment, it is recommended to use a photocoupler to isolate the equipment, and the specific withstand voltage value is determined according to actual needs.

Serial interface computer motherboard serial port

For serial transmission interface, it can only transmit 1Bit at a time. The serial port can be used to connect an external modem, plotter, or serial printer. It can also connect to network devices such as routers and switches in a console connection, mainly used to configure them.