Series 2000 Communications Handbook

Digital Communications HardwareSeries 2000 Communications Handbook2.8. WIRING RS422 OR 4-WIRE RS485To use RS422, buffer the RS232 port of the PC with a suitable RS232/RS422 converter.The KD485 or 261 Communications Converter unit is recommended for this purpose.Figure 2.6 shows connections for this unit. Instruments on a RS422 communicationnetwork should be chain connected and not star connected.To construct a cable for RS422 operation use a screened cable with two twisted pairs plus aseparate core for common. Although common or screen connections are not necessary, theiruse will significantly improve noise immunity.The terminals used for RS422 digital communications are listed in the table below.Standard Cable PC socket pin no. PC Function * Instrument Terminal InstrumentColour 25 way 902-4 2400 FunctionWhite 3 Receive (RX+) F1 HE Transmit(TX+)Black 16 Receive (RX-) F2 HF Transmit(TX-)Red 12 Transmit (TX+) F3 HB Receive(RX+)Black 13 Transmit (TX-) F4 HC Receive (RX-)Green 7 Common F5 HD CommonScreen 1 Ground• These are the functions normally assigned to socket pins. Please check your PC manualto confirm.2-8 Series 2000 Communications Handbook Part No HA026230 Issue 2.0 Feb-00