Chapter 4: Appendix D - RS-485/422 Option | 4-17 |
Line bias feature
During the operation of a half duplex, or multi-drop RS-485/422 connection, there are situations (time intervals) when there is NO "generator station" driving the wires that interconnect the various stations. During these intervals the connection is susceptible to electrical interference from outside sources. The RS-485/422 SLIM has fixed bias circuits to reduce the sensitivity to electrical interference when no "generator station" (TxD and RTS) is driving the cable. These bias circuits force the "receiver stations" (RxD and CTS) into a known state.
Line load options
RS-485/422 lines normally need some type of load to prevent an impedance mismatch that causes signal interference. The RS- 485/422 specification defines line termination loads placed on either end of a twisted pair cable segment. Please refer to Figure 17 as an example of a typical circuit for a RS-485 application.
Figure 17: Typical RS-485 circuit
Typical RS-485 Circuit |
G | R |
Station A | Station D |
|
G | R |
|
Station B | Station C |
where: G = generationg station R = receiving station
Intellicon-NT960/PCI User's Manual, ver. 0.02