Brief Introduction Of Serial Port Network Topology; Rs232 - odot DPM01 User Manual

7.2 Brief introduction of serial port network topology

7.2.1 RS232

RS232 is one of serial communication interfaces controlled by industry. It is widely
used to connect computer serial interface with peripherals. RS232 using a signal and a
signal transmission form, return lines were in the land of the three wire connection
mode, can realize full-duplex communications, the transmission signals for single
ended, the total transmission of easy to generate common-mode interference, so the
noise resistance is weak, the transmission distance is limited, RS232 interface
standards stipulated in the code element distortion maximum transmission distance is
less than 4% under the condition of standard values of 50 feet (15 meters) (more than
15 m long distance communication, need to adopt modem), the maximum
transmission distance is also associated with communication baud rate, in the process
of practical application, if the transmission distance is far, Please reduce the baud rate.
In order to reduce the electromagnetic interference from the outside during the signal
transmission, please use the shielded cable as the communication cable.
RS232 interface standard specifies that TXD and RXD:
RS232 USES negative logic to transmit signals and takes the signal of -(3~15) V as
logic "1". Take the signal of +(3~15) V as logical "0"; Voltages between -3 and +3V
are meaningless, as are voltages lower than -15V or higher than +15V.
RS232 Interface Classification:
DB9 header interface
The top left corner is 1, the bottom right corner is 9
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