The Modbus TCP interface on the DeltaV PK controller's local device network allows communication to/from Modbus TCP data sources such as drives, motor control centers, analyzers and similar devices.
A Modbus client can read and write data from/to Modbus servers (slave devices). Modbus server devices can be direct Modbus TCP devices or Modbus serial devices under a Modbus TCP gateway.
The Modbus TCP Port on the DeltaV PK controller is a Modbus server (a slave device). The DeltaV PK controller's PO1 is a Modbus TCP client (master). The two (server and client) ports cannot be switched.
The PO1 subsystem is disabled by default allowing you to configure the local device network without affecting the controller's overall integrity and without creating IP address conflicts during configuration.
Configuring the local device network involves setting a unique IP address and binding it to a physical Ethernet port on the PK controller. Configuration is performed in DeltaV Explorer on the PO1's Properties dialog's Advanced tab.
All reads will be performed periodically and outputs will be sent when they are written at a rate limited by the execution rate of the module writing the outputs.
Only the Modbus TCP standard protocol is supported.
The logical devices and signals defined under the Modbus device include the information needed to identify the specific Modbus device (for serial devices under a Modbus TCP gateway) and register being accessed.
The Modbus TCP polling rate depends directly on the number of physical devices, logical devices, and signals configured. The Modbus interface implementation scans the local device network at rates up to a scan cycle of 50 msec (this is the best possible speed).