Square D PM710-Modbus TRU and Wonderware

dear all,

any one know, how to communicate wonderware and Square D pm710 RTU module..this is having only RS485 port with + and - marked.I cant get it how to connect this with my PC side port r+,r-,S+ and S-, with DCE and DTE selection switch.

RTU module setting is addr.=1, baudrate=9600,parity=none,

Holding address starts at 4000.

thanksx

Apel said:

any one know, how to communicate wonderware and Square D pm710 RTU module..this is having only RS485 port with + and - marked.I cant get it how to connect this with my PC side port r+,r-,S+ and S-, with DCE and DTE selection switch.

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Your PM710 is a 2-wire RS485 device. The PC is a 4-wire device.

Your options are:

Simply wire the PC r+ to the s+ and R- to s- effectively creating a 2-wire connection. Notice this does not always work but I am not aware of it causing any problems. Sometimes a 120 Ohm resistor is needed across the PM710 terminals.

Or, what always works is a 2-wire to 4-wire convertor. You can get these from many places (Square D's is #CNV-100).

One place I used to go for RS485 applications was Robust DataCom at www.robustdc.com.