# Modbus Client Device – Tag Selected Path

The Modbus Client Device supports the Tag Selected Path feature of Cognex Designer. As such, it can be used to implement read and write operations for a Modbus Client.

The Selected Path format for the Modbus Client Device is the following:

[ClientDeviceName]'StorageIOType''StartAddress':UnitCount

The supported path keys, Storage IO Types and access types are listed below.

Storage IO Type | Selected Path Key | Supported Access
Coils | C | Read and Write
Discrete Inputs | DI | Read
Input Register | IR | Read
Holding Register | HR | Read and Write

See the below screenshot for examples:

Once the Selected Path has been set, an Update Rate property will become available for the tag, as shown below.

Use the Update Rate property to set the desired time (in milliseconds) for the tag to be polled from the Modbus Client Device.

Note: Any read or write operations that occur will update the tag or Modbus server storage during the next poll cycle.
Tip:

Once a Modbus Client Device Selected Path has been set for a tag, you can monitor the tag with the Communications Monitor when the project is in Test Mode.