Router Common interface

This paper takes Cisco router as an example, introduces the types, characteristics and application situations of common interfaces on routers.

1 Eia/tia 232

Eia/tia 232 is sometimes called the RS-232 c.rs (recommended Standard) on behalf of the recommended standards (EIA standards are generally referred to as "RS"), 232 is the identification number, C on behalf of the latest changes RS-232. It is by the American Electronics Association/Telecommunications Industry Association (ELECTRONIC Industries Association/telecommunications Industries association,eia/ TIA) announced in 1969 the standard of communication protocols. It was initially used primarily for communication between close-range DTE and DCE devices. It was later widely used in the near-earth connection standard between a computer's serial interface (COM1, COM2, etc.) and a terminal or peripheral. The standard in the data transmission rate of 20Kbps, the longest communication distance of 15 meters. The standards corresponding to the international standard is CCITT recommended standard v.24.

This standard describes the problems related to serial interface communication, such as the mechanical and electrical characteristics of cables, interfaces, signal functions and transmission process characteristics.

1.1 Mechanical Properties

RS-323 C can have several types of connectors (interfaces), such as 25-pin connectors (DB-25), 15-pin connectors (DB-15), and 9-pin connectors (DB-9). DB-25 and DB-9 are the most common, as shown in Figure 1. Regardless of the type of interface, the fluidly connector is defined to connect to the DTE device, and the pin-end connector is used to connect to the DCE device.

Figure 1 RS-232 interface type

1.2 Electrical Index

RS-232 c stipulates that the voltage range of the logic 1 on the data line is: -3v~-15v, the voltage range of logic 0 is: +3~+15v; the signal on the communication control line is valid or connected voltage range is: +3~+15v, Signal invalid or disconnected voltage range is: -3v~-15v. Other values are considered illegal.

1.3 Functional characteristics

Functional characteristics Specify the connector's definition of each pin, and which circuit connection, what function. Table 1 gives the definition and function of some of the needles commonly used in DB-25.

Table 1 Description of functional characteristics of RS-232 C

PIN number	Number code	Name	Function description
1	Aa	GND	Protected land
2	BA	TxD	Data send
3	Bb	Rxd	Data reception
4	Ca	Rts	Request Send
5	Cb	Cts	Allow send
6	Cc	Dsr	Data Settings ready.
7	Ab	GND	Signal Land
8	Cf	DCD	Carrier signal Detection
20	Cd	DTR	Data Terminal ready.
22	Ce	RI	Ringing indication

which

The 1th needle gnd, is the equipment protection, is connected with the equipment chassis.

The 2nd Pin TXD (transmitted data) is a data sending pin from which DTE sends data to DCE.

The 3rd pin RXD (Received data) is the data receiving pin from which the DTE receives data from DCE.

The 4th needle RTS (request to send) is used to indicate that a DTE request sends data to DCE.

The 5th Needle CTS (Clear to Send) is used to indicate that DCE is ready to receive data from DTE and is a response signal to the DTE request to send a signal RTS.

The 6th Pin DSR (Data Set Ready) is used to indicate that DCE has communicated with the communication channel, completes operational preparation, and is not in a test mode or disconnected mode.

8th Pin DCD (Data Carrier detect), carrier signal detection, DCE uses DCD pin to inform DTE of its connection with remote devices to establish and terminate the situation. For example, DCE notifies DTE by lowering the DCD signal that its connection to the remote device has terminated.

The 20th pin DTR (Data Terminal Ready) is used to indicate that the DTE is ready. This line is sometimes connected to the DTE power supply, and once the power is connected, there is a valid signal on the line.

The 22nd needle ri (ringing) is the ringing indicator. When a DCE receives a ringing call signal from the other DCE, it makes the signal valid (on state) and notifies the DTE that it has been called.