S7-1200 <-> S7-1200 Modbus via RS232

Homer_BL

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H

Join Date

Feb 2003

Posts

252

• Mar 16, 2011

• #1

Hi all!

If I want to connect two S7-1200 CPUs with RS232 ports on both CPUs, and implement a Modbus RTU communication,
what is the cable pinout of a connecting cable?

Thanks.

 

MikeDawkins

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M

Join Date

Sep 2005

Location

Somerset

Posts

39

• Mar 17, 2011

• #2

Standard RS232 pinout : 2 - 3, 3 - 2, 5 - 5
But why go to the expense of comms modulas when the cpu has ethernet built in

 

TurpoUrpo

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Join Date

May 2008

Location

Switzerland

Posts

1,571

• Mar 17, 2011

• #3

There is straight up example in siemens website for s7-1200 to s7-1200 modbus rtu comms with cp. But, I too wonder why modbus when there is ethernet integrated.