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DeltaV to DeltaV via Modbus RTU - serial Card, half duplex

Hi All,

we are going to implement a DeltaV to DeltaV communication via MODBUS RTU. For development purpose we have a SX with two serial cards connected to the development system.

They are wired between 1-1, 2-4, 4-2. The cards are flased to 1.55 (the system is 13.3.1). half duplex, 9600, odd,

Card 1 is Master, 1 Device Address 2

Card 3 is Slave, 1 Device Address 3

Same card configuration 

I just configured  one boolean as output on card 1 and same boolean on card 3 as input. 

Card 1 - Not communicating

Card 2 - 5% Comm Error

Every help is welcome to understand the issue here.

Thanks a lot,

Manuel

Manuel Behrens
  • Jason.Brumfield
    First thing I would check is to make sure you have the interface wiring correct on both serial cards. Second make sure you didn't exceed the cable length limitation of 232.
  • Invalid String
    I would start by verifying the settings at the port level on the card.
    Ensure it is enabled and then check the communications tab to make sure your properties are identical between the cards.

    Can you query the Modbus slave using other software like Baseblock Com Test pro, simply modbus, modsak, or similar?
    This should help to identify if the slave is responding to queries.
  • Manuel Behrens
    Thank a lot! The issue was, different device addresses for the same slave. One master site, you are defining the slave and on the slave site you are defining the slave too.

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