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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