Chengdu Ebyte Electronic Technology Co.,Ltd E851-RTU(4440-ETH) User Manual
Copyright ©2012–2019, Chengdu Ebyte Electronic Technology Co.,Ltd
1. Quick Start
This chapter is a quick introduction to E851-RTU (4440-ETH) series products. It is recommended that users read this
chapter systematically and operate it according to the instructions. It will have a systematic understanding of the module
products. Users can also choose the chapters you are interested in to read according to their needs. For specific details
and instructions, please refer to the following chapters.
1.1. Port connection
1.1.1. RS485 connection
Note: When the 485 bus high frequency signal is transmitted, the signal wavelength is shorter than the transmission line.
The reflected wave will form at the terminal of the transmission line and interfere with the original signal. Therefore,
terminal resistance should be added at the end of the transmission line so that the signal will not reflect when it reaches
the end of the transmission line. The terminal resistance should be the same as the impedance of the communication
cable with a typical value of 120 ohms. Its function is to match the bus impedance and improve the anti-interference and
reliability of data communication.
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