B&B Electronics Asynchronous to Synchronous Converter 2010 Uživatelský manuál stáhnout pdf (Strana 14)

Department of Computer Science and Electronics

reduce electrical noise sensitivity. The value of each termination resistor should be

equal to the cable impedance (typically, 120 ohms for twisted pairs). Star and ring

topologies are not recommended because of signal reflections or excessively low or

high termination impedance.

Figure 2-9 shows the potentials of the '+' and '−' pins of an RS-485 line during

transmission of an RS-485 byte:

The table below illustrates a summary of the RS485 characteristic.

Figure 2-9. RS-485 byte transmission

Figure 2-10. RS-485 network characteristic

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 42 43

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B&B Electronics Asynchronous to Synchronous Converter 2010 Uživatelský manuál Strana 14