Worth Data 5000 owner manual Appendix N RS-422, Table N-1. RS-422 Multi-drop cable

Appendix N: RS-422

Using the TriCoder with an RS-422 board instead of a standard RS-232 serial port allows multiple TriCoders to be multi-dropped off of a single RS-422 port at a distance up to 4000 feet. Multiple TriCoders can then be polled periodically while they are collecting data. To be used with a RS-422 board, the TriCoder must have the 422 option factory installed. This is available by special order only.

RS-422 boards are available from a variety of sources. The specifications vary for different RS-422 boards, so make sure you have proper documentation for your board.

The biggest problem we see with RS-422 multi-dropping has to do with cabling. Follow the specifications for the cabling exactly as they are shown. Use only the wire specified (don‟t use whatever is lying around) and be sure to test your communications thoroughly before going on-line with a large installation.

You can use the following pin-outs to create your own RS-422 multi-drop cables: Tying T+ on the TriCoder end to the R+ on the continuous 422 line.

Tying T- on the TriCoder end to the R- on the continuous 422 line.

Function		30 Pin
Transmit Data +	(T+)	21
Transmit Data -	(T-)	22
Ground		20
Receive Data +	(R+)	23
Receive Data -	(R-)	24

Table N-1. RS-422 Multi-drop cable

You must have T+/T- in one twisted pair and R+/R- in the other.

At the end of the string of TriCoders, tie pins 2&3 and 5&6 together with 120 ohm resistors as a 422 terminator plug. Use Belden 1227AI or Cat 5 wire for all of the 422 cabling above.

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