User Manual

Appendix D RS-485 Network 61

Since this value lies within 10% of the line characteristic impedance.

Thus as already stated above the line termination resistor R

will normal-

ly equal the characteristic impedance Z

The star connection causes a multitude of these discontinuities since

there are several transmission lines and is therefore not recommend.

☛

Note: The recommend method wiring method, that causes a min-

imum amount of reflection, is daisy chaining where all re-

ceivers tapped from one transmission line needs only to

be terminated twice.

D.3 RS-485 Data Flow Control

The RS-485 standard uses a single pair of wires to send and receive data.

This line sharing requires some method to control the direction of the

data flow. RTS (Request To Send) and CTS (Clear To Send) are the most

commonly used methods.

Figure D-7: RS-485 data flow control with RTS