Ebyte E831-RTU(8080T-485), Руководство пользователя

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1.1. Port connection
1.1.1. RS485 Connection
Note: When transmitting high-frequency signals on the 485 bus, the signal wavelength is shorter than
the transmission line. The signal will form reflected waves at the end of the transmission line and
interfere with the original signal. Therefore, a terminating resistor must be added at the end of the
transmission line so that the signal does not reflect after reaching the end of the transmission line. The
termination resistance should be the same as the impedance of the communication cable, with a typical
value of 120 ohms. Its role is to match the impedance of the bus to improve the anti-interference and
reliable performance of data communication.