Series 2000 Communications Handbook - Soliton

Digital Communications HardwareSeries 2000 Communications Handbook2.10. WIRING RS422 AND RS485 CONTROLLERSIt is generally not possible to mix controllers using a 2-wire and 4-wire standards. However,in some cases it may be required to add new controllers (such as 2000 series on 2-wirecomms) to an existing installation with controllers on 4-wire comms.In these cases the existing communications link may be modified by adding a special versionof the KD485 converter unit, supplied as KD485-ADE 422-422. Figure 2-4 shows a largesystem of controllers using a mixture of both standards.The standard KD485 unit converts from 232 to 4-wire 485 and this link is used tocommunicate to the first 32 existing controllers. The second KD485 is the special versionwhich converts from 4-wire to 4-wire communications to communicate with a further bank of32 controllers on 4-wire communications. The third KD485 is the same special version whichis connected to convert from 4-wire to 2-wire communications. It’s input side behaves to the4-wire link as another controller would on an existing system, whilst at the same time thecommunications messages from the computer are passed onto the output side of this unit.This is connected to the 2-wire communications link, that will contain the series 2000controllers. Any responses from controllers on this link will cause data to be placed on to the4-wire link and thence will be passed back to the computer.2-12 Series 2000 Communications Handbook Part No HA026230 Issue 2.0 Feb-00