computer
use
Connecting wire connection
You can communicate, or you can connect some expansion devices with serial ports.
In order to realize serial communication, PC usually has two serial interfaces conforming to RS-232C standard, and a serial controller composed of universal asynchronous transceiver control chip UART is used to handle the sending and receiving of serial data. The serial port on PC usually uses a 25-core or 9-core DB-25 or DB-9 connector, which is mainly used to connect MODEM equipment, so the RS-232C standard stipulates many special interface leads for modems.
At present, the commonly used RS232 serial ports are 9-pin D-shaped serial port [DB9] and 25-pin D-shaped serial port [DB25], and the maximum communication distance is [15m]. When the distance between two devices is very close, 232 cable can be used to directly connect their 232 serial ports; If the distance is far, you can connect through a modem.
RS232 interface—
● Adopt "negative logic"-the output terminal uses +5v ~+ 15v for [logic 0] and -5v ~- 15v for [logic 1].
● Adopt "single-ended driving"-output the driving level through the data transmitter [TD], and take the signal ground GND as the reference point.
● Adopt "single-ended reception"-input the reception level through the data receiving terminal [RD], and take the signal ground GND as the reference point.
RS232 three-wire system—
To realize point-to-point two-way communication, three communication lines are needed. The data sending end [TD] of the master is connected with the data receiving end [RD] of the slave, and the signal ground [GND] of both sides is directly connected.
Precautions for using RS232—
RS232 serial port cannot be directly connected with RS485 serial port-because their electrical standards are different; There are various serial converters on the market, which must be connected through converters. In addition, don't plug the serial port with electricity. At least one end is powered off when plugging and unplugging, otherwise it is easy to damage the serial port.